(* Contribution to the Coq Library   V6.3 (July 1999)                    *)
(***************************************************************************)
(* File: applications.v                                                    *)
(* auteur: alex@sysal.ibp.fr                                               *)
(* date: 19/10/95                                                          *)
(***************************************************************************)
Require Export couples.
(***************************************************************************)
(***************************************************************************)
(* Relations n-aires                                                       *)
(***************************************************************************)
(***************************************************************************)
Definition n_aire (n : nat) (a : E) (F : E -> Prop) :=
subset F (cart_power n a).
(* Pas de reciproque (dixit pagano pb des ensembles non decidables)        *)
(* Proof of lem_subset                                                     *)
intros; elim (axs_comprehension F b y); intros.
generalize H1; rewrite <- H; clear H H1 H2; intros.
elim H1; intros; auto with zfc.
Qed.
(* End of proof of lem_subset                                              *)
(***************************************************************************)
(***************************************************************************)
(* applications                                                            *)
(***************************************************************************)
(***************************************************************************)
Definition fun_ (f : E) :=
(exists a : E, (exists b : E, inc f (cartesien a b))) /\
(forall x y z : E, In (couple x y) f -> In (couple x z) f -> y = z).
(***************************************************************************)
(* Domaine d'une application                                               *)
(***************************************************************************)
Definition dom (f : E) :=
subset (fun v0 : E => fun_ f -> exists v1 : E, In (couple v0 v1) f)
(reunion (reunion f)).
(***************************************************************************)
(* Image d'une application                                                 *)
(***************************************************************************)
Definition Img (f : E) :=
subset (fun v1 : E => fun_ f -> exists v0 : E, In (couple v0 v1) f)
(reunion (reunion f)).
(***************************************************************************)
(* f est une application de a vers b                                       *)
(***************************************************************************)
Definition fun_sig (f a b : E) := fun_ f /\ dom f = a /\ inc (Img f) b.
(* Proof of lem_fun_sig_is_fun                                             *)
unfold fun_sig in |- *; intros.
elim H; clear H; intros; auto with zfc.
Qed.
(* End of proof of lem_fun_sig_is_fun                                      *)
(* Proof of lem_fun_sig_dom                                                *)
intros; elim H; clear H; intros; elim H0; clear H0; intros; auto with zfc.
Qed.
(* End of proof of lem_fun_sig_dom                                         *)
(* Proof of lem_fun_sig_img                                                *)
intros; elim H; clear H; intros; elim H0; clear H0; intros; auto with zfc.
Qed.
(* End of proof of lem_fun_sig_img                                         *)
(***************************************************************************)
(* f est une application surjective de a vers b                            *)
(***************************************************************************)
Definition fun_surj (f a b : E) := fun_ f /\ dom f = a /\ Img f = b.
(***************************************************************************)
(* f est une application injective                                         *)
(***************************************************************************)
Definition fun_inj (f a b : E) :=
fun_ f /\
dom f = a /\
inc (Img f) b /\
(forall b : E, In b (Img f) -> exUniq _ (fun a : E => In (couple a b) f)).
(***************************************************************************)
(* f est une bijection                                                     *)
(***************************************************************************)
Definition fun_bij (f a b : E) :=
fun_ f /\
dom f = a /\
Img f = b /\
(forall b : E, In b (Img f) -> exUniq _ (fun a : E => In (couple a b) f)).
(* Proof of lem_surj_to_sig                                                *)
unfold fun_surj in |- *; unfold fun_sig in |- *; intros.
elim H; clear H; intros; elim H0; clear H0; intros.
split;
[ auto with zfc
| split; [ auto with zfc | unfold inc in |- *; intros ] ].
generalize H2; rewrite H1; tauto.
Qed.
(* End of proof of lem_surj_to_sig                                         *)
(* Proof of lem_inj_to_sig                                                 *)
unfold fun_inj in |- *; unfold fun_sig in |- *; intros.
elim H; clear H; intros; elim H0; clear H0; intros; elim H1; clear H1; intros.
split; [ auto with zfc | split; auto with zfc ].
Qed.
(* End of proof of lem_inj_to_sig                                          *)
(* Proof of lem_bij_to_sig                                                 *)
unfold fun_bij in |- *; unfold fun_sig in |- *; intros.
elim H; clear H; intros; elim H0; clear H0; intros; elim H1; clear H1; intros.
split;
[ auto with zfc
| split; [ auto with zfc | unfold inc in |- *; intros ] ].
rewrite <- H1; auto with zfc.
Qed.
(* End of proof of lem_bij_to_sig                                          *)
(* Proof of lem_bij_is_inj                                                 *)
unfold fun_bij, fun_inj in |- *; intros.
elim H; clear H; intros; elim H0; clear H0; intros; elim H1; clear H1; intros.
split;
[ auto with zfc
| split;
[ auto with zfc
| split;
[ unfold inc in |- *; intros; rewrite <- H1; auto with zfc
| auto with zfc ] ] ].
Qed.
(* End of proof of lem_bij_is_inj                                          *)
(* Proof of lem_bij_is_inj                                                 *)
unfold fun_bij, fun_surj in |- *; intros.
elim H; clear H; intros; elim H0; clear H0; intros; elim H1; clear H1; intros.
split; [ auto with zfc | split; auto with zfc ].
Qed.
(* End of proof of lem_bij_is_inj                                          *)
(* Proof of lem_inj_surj_is_bij                                            *)
unfold fun_surj, fun_inj, fun_bij in |- *; intros.
elim H; clear H; intros; clear H; elim H1; clear H1; intros; clear H.
elim H0; clear H0; intros; elim H0; clear H0; intros; elim H2; clear H2;
intros.
split;
[ auto with zfc
| split; [ auto with zfc | split; auto with zfc ] ].
Qed.
(* End of proof of lem_inj_surj_is_bij                                     *)
(***************************************************************************)
(***************************************************************************)
(* L'application Vide                                                      *)
(***************************************************************************)
(***************************************************************************)
(* Proof of lem_vide_application                                           *)
unfold fun_ in |- *; split;
[ exists Vide; exists Vide; exact (lem_vide_is_inc (cartesien Vide Vide))
| intros ].
unfold Vide in H; elim (lem_vide_propertie (couple x y) var_vide);
auto with zfc.
Qed.
(* End of proof of lem_vide_application                                    *)
(* Proof of lem_dom_vide                                                   *)
apply axs_extensionnalite; intros; unfold iff in |- *; split; intros;
unfold dom in H.
elim
(axs_comprehension
(fun v0 : E => fun_ Vide -> exists v1 : E, In (couple v0 v1) Vide)
(reunion (reunion Vide)) v2); intros; generalize (H0 H);
clear H H0 H1; intros.
generalize H; rewrite lem_reunion_vide; rewrite lem_reunion_vide; tauto.
elim (lem_vide_propertie v2 var_vide); auto with zfc.
Qed.
(* End of proof of  lem_dom_vide                                           *)
(* Proof of lem_img_vide                                                   *)
apply axs_extensionnalite; intros; unfold iff in |- *; split; intros;
unfold Img in H.
elim
(axs_comprehension
(fun v1 : E => fun_ Vide -> exists v0 : E, In (couple v0 v1) Vide)
(reunion (reunion Vide)) v2); intros; generalize (H0 H);
clear H H0 H1; intros.
elim H; clear H; intros.
generalize H; rewrite lem_reunion_vide; rewrite lem_reunion_vide; tauto.
unfold Vide in H; elim (lem_vide_propertie v2 var_vide); auto with zfc.
Qed.
(* End of proof of lem_img_vide                                            *)
(* Proof of lem_fun_vide_sig                                               *)
unfold fun_sig in |- *; intros.
split;
[ exact lem_vide_application
| split;
[ exact lem_dom_vide | rewrite lem_img_vide; exact (lem_vide_is_inc a) ] ].
Qed.
(* End of proof of lem_fun_vide_sig                                        *)
(* Proof of lem_fun_and_dom                                                *)
intros; unfold dom in |- *.
elim
(axs_comprehension
(fun v0 : E => fun_ f -> exists v1 : E, In (couple v0 v1) f)
(reunion (reunion f)) a); intros; apply H2; clear H1 H2;
intros.
split; [ idtac | intros; exists b; auto with zfc ].
elim (axs_reunion (reunion f) a); intros; apply H2; clear H1 H2; intros.
exists (singleton a); split; [ idtac | exact (lem_x_in_sing_x a) ].
elim (axs_reunion f (singleton a)); intros; apply H2; clear H1 H2; intros.
exists (couple a b); split;
[ auto with zfc
| unfold couple in |- *;
elim (axs_paire (singleton a) (paire a b) (singleton a));
intros; apply H2; left; reflexivity ].
Qed.
(* End of proof of lem_fun_and_dom                                         *)
(* Proof of lem_fun_and_img                                                *)
intros; unfold Img in |- *.
elim
(axs_comprehension
(fun v1 : E => fun_ f -> exists v0 : E, In (couple v0 v1) f)
(reunion (reunion f)) b); intros; apply H2; clear H1 H2;
intros.
split; [ idtac | intros; exists a; auto with zfc ].
elim (axs_reunion (reunion f) b); intros; apply H2; clear H1 H2; intros;
exists (paire a b).
split;
[ idtac | elim (axs_paire a b b); intros; apply H2; right; reflexivity ].
elim (axs_reunion f (paire a b)); intros; apply H2; clear H1 H2; intros.
exists (couple a b); split;
[ auto with zfc
| unfold couple in |- *;
elim (axs_paire (singleton a) (paire a b) (paire a b));
intros; apply H2; right; reflexivity ].
Qed.
(* End of proof of lem_fun_and_img                                         *)
(* Proof of lem_App                                                   *)
intros; unfold dom in H0.
elim
(axs_comprehension
(fun v0 : E => fun_ f -> exists v1 : E, In (couple v0 v1) f)
(reunion (reunion f)) x); intros; generalize (H1 H0);
clear H0 H1 H2; intros.
elim H0; clear H0; intros; generalize (H1 H); clear H1; intros.
elim H1; clear H1; intros.
exists x0; split; [ exact (lem_fun_and_img f x x0 H H1) | auto with zfc ].
Qed.
(* End of proof of lem_App                                            *)
(* Proof of lem_App_rev                                               *)
intros; unfold Img in H0.
elim
(axs_comprehension
(fun v1 : E => fun_ f -> exists v0 : E, In (couple v0 v1) f)
(reunion (reunion f)) y); intros; generalize (H1 H0);
clear H0 H1 H2; intros.
elim H0; clear H0; intros; generalize (H1 H); clear H1; intros; elim H1;
clear H1; intros.
exists x; split; [ exact (lem_fun_and_dom f x y H H1) | auto with zfc ].
Qed.
(* End of proof of lem_App_rev                                        *)
(***************************************************************************)
(***************************************************************************)
(* Composition d'application                                               *)
(***************************************************************************)
(***************************************************************************)
Definition comp (f g a b c : E) (Af : fun_sig f a b)
(Ag : fun_sig g b c) :=
subset
(fun c : E =>
exists y : E, In (couple (first c) y) f /\ In (couple y (second c)) g)
(cartesien a c).
(***************************************************************************)
(* Il peut paraitre necessaire de reformuler la definition de la           *)
(* composition.                                                            *)
(***************************************************************************)
Definition comp2 (f g a b c : E) :=
subset
(fun x : E =>
fun_sig f a b ->
fun_sig g b c ->
exists y : E, In (couple (first x) y) f /\ In (couple y (second x)) g)
(cartesien a c).
(* Proof of lem_comp2_eq_comp                                              *)
intros; apply axs_extensionnalite; unfold iff in |- *; split; intros.
unfold comp in H.
elim
(axs_comprehension
(fun c0 : E =>
exists y : E, In (couple (first c0) y) f /\ In (couple y (second c0)) g)
(cartesien a c) v2); intros; generalize (H0 H);
clear H H0 H1; intros.
elim H; clear H; intros; elim H0; clear H0; intros; elim H0; clear H0; intros.
unfold comp2 in |- *.
elim
(axs_comprehension
(fun x : E =>
fun_sig f a b ->
fun_sig g b c ->
exists y : E, In (couple (first x) y) f /\ In (couple y (second x)) g)
(cartesien a c) v2); intros; apply H3; clear H2 H3;
intros.
split; [ auto with zfc | intros; exists x; split; auto with zfc ].
unfold comp2 in H.
elim
(axs_comprehension
(fun x : E =>
fun_sig f a b ->
fun_sig g b c ->
exists y : E, In (couple (first x) y) f /\ In (couple y (second x)) g)
(cartesien a c) v2); intros; generalize (H0 H);
clear H H0 H1; intros.
elim H; clear H; intros.
elim (H0 Af Ag); clear H0; intros; elim H0; clear H0; intros.
unfold comp in |- *.
elim
(axs_comprehension
(fun c0 : E =>
exists y : E, In (couple (first c0) y) f /\ In (couple y (second c0)) g)
(cartesien a c) v2); intros; apply H3; clear H2 H3;
intros.
split; [ auto with zfc | exists x; split; auto with zfc ].
Qed.
(* End of proof of lem_comp2_eq_comp                                       *)
(* Proof of lem_comp_is_fun                                                *)
intros.
unfold fun_ in |- *; split; [ exists a; exists c | intros ].
unfold inc in |- *; intros.
unfold comp in H.
elim
(axs_comprehension
(fun c0 : E =>
exists y : E, In (couple (first c0) y) f /\ In (couple y (second c0)) g)
(cartesien a c) v0); intros; generalize (H0 H);
clear H H0 H1; intros.
elim H; clear H; intros; elim H0; clear H0; intros; elim H0; clear H0; intros.
unfold fun_sig in Af; unfold fun_sig in Ag.
elim Af; clear Af; intros.
elim H3; clear H3; intros.
elim Ag; clear Ag; intros.
elim H6; clear H6; intros.
auto with zfc.
unfold comp in H; unfold comp in H0.
elim
(axs_comprehension
(fun c0 : E =>
exists y0 : E,
In (couple (first c0) y0) f /\ In (couple y0 (second c0)) g)
(cartesien a c) (couple x y)); intros; generalize (H1 H);
clear H H1 H2; intros.
elim
(axs_comprehension
(fun c0 : E =>
exists y : E, In (couple (first c0) y) f /\ In (couple y (second c0)) g)
(cartesien a c) (couple x z)); intros; generalize (H1 H0);
clear H0 H1 H2; intros.
elim H; clear H; intros; elim H1; clear H1; intros; elim H1; clear H1; intros.
elim H0; clear H0; intros; elim H3; clear H3; intros; elim H3; clear H3;
intros.
generalize H3; clear H3; rewrite (lem_first_propertie x z); intros.
generalize H4; clear H4; rewrite (lem_second_propertie x z); intros.
generalize H1; clear H1; rewrite (lem_first_propertie x y); intros.
generalize H2; clear H2; rewrite (lem_second_propertie x y); intros.
unfold fun_sig in Af; elim Af; intros.
unfold fun_sig in Ag; elim Ag; intros.
unfold fun_ in H5; unfold fun_ in H7; clear H6 H8.
elim H5; clear H5; intros; clear H5.
elim H7; clear H7; intros; clear H5.
generalize (H6 x x0 x1 H1 H3); clear H1 H3; intros.
generalize H4; clear H4; rewrite <- H1; clear H1; intros.
exact (H7 x0 y z H2 H4).
Qed.
(* End of proof of lem_comp_is_fun                                         *)
(* Proof of lem_comp_dom                                                   *)
intros; apply axs_extensionnalite; intros; unfold iff in |- *; split; intros.
unfold dom in H.
elim
(axs_comprehension
(fun v0 : E =>
fun_ (comp f g a b c Af Ag) ->
exists v1 : E, In (couple v0 v1) (comp f g a b c Af Ag))
(reunion (reunion (comp f g a b c Af Ag))) v2);
intros; generalize (H0 H); clear H H0 H1; intros.
elim H; clear H; intros.
generalize (H0 (lem_comp_is_fun f g a b c Af Ag)); clear H0; intros.
elim H0; clear H0; intros.
unfold comp in H0.
elim
(axs_comprehension
(fun c0 : E =>
exists y : E, In (couple (first c0) y) f /\ In (couple y (second c0)) g)
(cartesien a c) (couple v2 x)); intros; generalize (H1 H0);
clear H0 H1 H2; intros.
elim H0; clear H0; intros; elim H1; clear H1; intros; elim H1; clear H1;
intros.
generalize H1; clear H1 H2; rewrite (lem_first_propertie v2 x); intros.
unfold fun_sig in Af; elim Af; intros.
exact (lem_fun_and_dom f v2 x0 H2 H1).
generalize Af Ag; intros.
unfold fun_sig in Af0; unfold fun_sig in Ag0.
elim Af; clear Af; intros; elim H1; clear H1; intros.
elim Ag; clear Ag; intros; elim H4; clear H4; intros.
generalize (lem_App f v2 H0 H); intros; elim H6; clear H6; intros; elim H6;
clear H6; intros.
unfold inc in H2.
generalize (H2 x); intros.
generalize (H8 H6); clear H6 H8; intros.
cut (In x (dom g)); [ intros | rewrite H4; auto with zfc ].
generalize (lem_App g x H3 H8); intros.
elim H9; clear H9; intros; elim H9; clear H9; intros.
unfold dom in |- *.
elim
(axs_comprehension
(fun v0 : E =>
fun_ (comp f g a b c Af0 Ag0) ->
exists v1 : E, In (couple v0 v1) (comp f g a b c Af0 Ag0))
(reunion (reunion (comp f g a b c Af0 Ag0))) v2);
intros; apply H12; clear H11 H12; intros.
split.
elim (axs_reunion (reunion (comp f g a b c Af0 Ag0)) v2); intros; apply H12;
clear H11 H12; intros.
exists (singleton v2); split; [ idtac | apply lem_x_in_sing_x ].
elim (axs_reunion (comp f g a b c Af0 Ag0) (singleton v2)); intros; intros;
apply H12; clear H11 H12; intros.
exists (couple v2 x0); split;
[ idtac
| unfold couple in |- *;
elim (axs_paire (singleton v2) (paire v2 x0) (singleton v2));
intros; apply H12; left; reflexivity ].
unfold comp in |- *.
elim
(axs_comprehension
(fun c0 : E =>
exists y : E, In (couple (first c0) y) f /\ In (couple y (second c0)) g)
(cartesien a c) (couple v2 x0)); intros; apply H12;
clear H11 H12; intros.
split; [ idtac | exists x ].
elim (lem_cartesian_propertie a c (couple v2 x0)); intros; apply H12;
clear H11 H12; intros.
exists v2; exists x0.
rewrite <- H1; split; [ auto with zfc | split; [ idtac | reflexivity ] ].
unfold inc in H5; generalize (H5 x0); intros; exact (H11 H9).
rewrite (lem_first_propertie v2 x0); rewrite (lem_second_propertie v2 x0);
split; auto with zfc.
intros; exists x0.
unfold comp in |- *.
elim
(axs_comprehension
(fun c0 : E =>
exists y : E, In (couple (first c0) y) f /\ In (couple y (second c0)) g)
(cartesien a c) (couple v2 x0)); intros; apply H13;
clear H12 H13; intros.
split; [ idtac | exists x ].
elim (lem_cartesian_propertie a c (couple v2 x0)); intros; apply H13;
clear H12 H13; intros.
exists v2; exists x0.
rewrite <- H1; split; [ auto with zfc | split; [ idtac | reflexivity ] ].
unfold inc in H5; generalize (H5 x0); intros; exact (H12 H9).
rewrite (lem_first_propertie v2 x0); rewrite (lem_second_propertie v2 x0);
split; auto with zfc.
Qed.
(* End of proof of lem_comp_dom                                            *)
(* Proof of lem_comp_img                                                   *)
intros; unfold inc in |- *; intros.
elim Af; intros; elim H1; clear H1; intros.
elim Ag; intros; elim H4; clear H4; intros.
elim
(lem_App_rev (comp f g a b c Af Ag) v0 (lem_comp_is_fun f g a b c Af Ag) H);
intros.
elim H6; clear H6; intros.
unfold comp in H7.
elim
(axs_comprehension
(fun c0 : E =>
exists y : E, In (couple (first c0) y) f /\ In (couple y (second c0)) g)
(cartesien a c) (couple x v0)); intros; generalize (H8 H7);
clear H7 H8 H9; intros.
elim H7; clear H7; intros; elim H8; clear H8; intros; elim H8; clear H8;
intros.
generalize H9; clear H9; rewrite (lem_second_propertie x v0); intros.
exact (lem_fun_and_img g x0 v0 H3 H9).
Qed.
(* End of proof of lem_comp_img                                            *)
(* Proof of lem_comp_make                                                  *)
intros; unfold comp in |- *.
elim
(axs_comprehension
(fun c0 : E =>
exists y : E, In (couple (first c0) y) f /\ In (couple y (second c0)) g)
(cartesien a c) (couple x z)); intros; apply H2;
clear H1 H2; intros.
split;
[ idtac
| exists y; rewrite (lem_first_propertie x z);
rewrite (lem_second_propertie x z); split; auto with zfc ].
elim Af; clear Af; intros; elim H2; clear H2; intros.
elim Ag; clear Ag; intros; elim H5; clear H5; intros.
elim (lem_cartesian_propertie a c (couple x z)); intros; apply H8;
clear H7 H8; intros.
exists x; exists z; split;
[ rewrite <- H2; exact (lem_fun_and_dom f x y H1 H)
| split; [ idtac | reflexivity ] ].
generalize (lem_fun_and_img g y z H4 H0); intros.
unfold inc in H6; exact (H6 z H7).
Qed.
(* End of proof of lem_comp_make                                           *)
(* Proof of lem_comp_intermed                                              *)
intros; unfold comp in H.
elim
(axs_comprehension
(fun c0 : E =>
exists y : E, In (couple (first c0) y) f /\ In (couple y (second c0)) g)
(cartesien a c) (couple x z)); intros; generalize (H0 H);
clear H H0 H1; intros.
elim H; clear H; intros; elim H0; clear H0; intros; elim H0; clear H0; intros.
generalize H0; clear H0; rewrite (lem_first_propertie x z); intros.
generalize H1; clear H1; rewrite (lem_second_propertie x z); intros.
exists x0; split; auto with zfc.
Qed.
(* End of proof of lem_comp_intermed                                       *)
(***************************************************************************)
(***************************************************************************)
(* Redefinissons maintenant une application dans le style f(x) = y         *)
(***************************************************************************)
(***************************************************************************)
Definition App (f : E) (Af : fun_ f) (x : E) :=
subset (fun z : E => exists y : E, In (couple x y) f /\ In z y)
(reunion (Img f)).
(* Proof of lem_eval_propertie                                             *)
intros; apply axs_extensionnalite; intros.
unfold iff in |- *; split; intros; unfold App in |- *.
elim
(axs_comprehension (fun z : E => exists y : E, In (couple x y) f /\ In z y)
(reunion (Img f)) v2); intros; apply H2; clear H1 H2;
intros.
split; [ idtac | exists y; split; auto with zfc ].
elim (axs_reunion (Img f) v2); intros; apply H2; clear H1 H2; intros.
exists y; split; [ exact (lem_fun_and_img f x y Af H) | auto with zfc ].
unfold App in H0.
elim
(axs_comprehension (fun z : E => exists y : E, In (couple x y) f /\ In z y)
(reunion (Img f)) v2); intros; generalize (H1 H0);
clear H0 H1 H2; intros.
elim H0; clear H0; intros; elim H1; clear H1; intros; elim H1; clear H1;
intros.
elim Af; clear Af; intros; elim H3; clear H3; intros; elim H3; clear H3;
intros.
generalize (H4 x x0 y H1 H); clear H4; intros.
rewrite <- H4; auto with zfc.
Qed.
(* End of proof of lem_eval_propertie                                      *)
(* Proof of lem_eval_prop2                                                 *)
unfold dom in |- *; intros.
elim
(axs_comprehension
(fun v0 : E => fun_ f -> exists v1 : E, In (couple v0 v1) f)
(reunion (reunion f)) x); intros; generalize (H0 H);
clear H H0 H1; intros.
elim H; clear H; intros.
generalize (H0 Af); clear H0; intros; elim H0; clear H0; intros.
generalize (lem_eval_propertie f x x0 Af H0); intros.
rewrite <- H1; auto with zfc.
Qed.
(* End of proof of lem_eval_prop2                                          *)
(* Proof of lem_x_in_fun_form                                              *)
intros.
elim Af; clear Af; intros.
elim H0; clear H0; intros; elim H0; clear H0; intros.
generalize (H0 x H); clear H H0; intros.
elim (lem_cartesian_propertie x0 x1 x); intros; generalize (H0 H);
clear H H0 H2; intros.
elim H; clear H; intros; elim H; clear H; intros; elim H; clear H; intros;
elim H0; clear H0; intros.
exists x2; exists x3; auto with zfc.
Qed.
(* End of proof of lem_x_in_fun_form                                       *)
(***************************************************************************)
(***************************************************************************)
(* Image d'une partie du domaine d'une application f par f                 *)
(***************************************************************************)
(***************************************************************************)
Definition fun_img_directe (f : E) (Af : fun_ f) (c : E) :=
subset
(fun x : E =>
In c (parties (dom f)) -> exists y : E, In y c /\ x = App f Af y)
(Img f).
(***************************************************************************)
(* On peut definir l'image reciproque d'une partie de l'image d'une        *)
(* application f.                                                          *)
(***************************************************************************)
Definition fun_img_inverse (f : E) (Af : fun_ f) (d : E) :=
subset (fun x : E => In d (parties (Img f)) -> In (App f Af x) d) (dom f).
(***************************************************************************)
(* Ces deux notions permettent de definir une application des parties de   *)
(* (dom f) dans les parties de (Img f)                                     *)
(***************************************************************************)
Definition fun_part (f : E) (Af : fun_ f) :=
subset (fun x : E => exists y : E, x = couple y (fun_img_directe f Af y))
(cartesien (parties (dom f)) (parties (Img f))).
(* Proof of lem_fun_part_is_fun                                             *)
intros; unfold fun_ in |- *; split; intros.
exists (parties (dom f)); exists (parties (Img f)); unfold inc in |- *;
intros.
unfold fun_part in H.
elim
(axs_comprehension
(fun x : E => exists y : E, x = couple y (fun_img_directe f Af y))
(cartesien (parties (dom f)) (parties (Img f))) v0);
intros; generalize (H0 H); clear H H0 H1; intros.
elim H; clear H; intros; auto with zfc.
unfold fun_part in H; unfold fun_part in H0.
elim
(axs_comprehension
(fun x0 : E => exists y0 : E, x0 = couple y0 (fun_img_directe f Af y0))
(cartesien (parties (dom f)) (parties (Img f)))
(couple x y)); intros; generalize (H1 H); clear H H1 H2;
intros.
elim H; clear H; intros; elim H1; clear H1; intros.
elim
(axs_comprehension
(fun x0 : E => exists y : E, x0 = couple y (fun_img_directe f Af y))
(cartesien (parties (dom f)) (parties (Img f)))
(couple x z)); intros; generalize (H2 H0); clear H0 H2 H3;
intros.
elim H0; clear H0; intros; elim H2; clear H2; intros.
elim (lem_couple_propertie x x0 y (fun_img_directe f Af x0)); intros;
generalize (H3 H1); clear H1 H3 H4; intros.
elim H1; clear H1; intros.
rewrite H3; clear H3; rewrite <- H1; clear H1.
elim (lem_couple_propertie x x1 z (fun_img_directe f Af x1)); intros;
generalize (H1 H2); clear H2 H3 H1; intros.
elim H1; clear H1; intros.
rewrite H2; clear H2; rewrite <- H1; clear H1; reflexivity.
Qed.
(* End of proof of lem_fun_part_is_fun                                     *)
(* Proof of lem_fun_part_dom                                               *)
intros; apply axs_extensionnalite; intros.
unfold iff in |- *; split; intros.
unfold dom in H.
elim
(axs_comprehension
(fun v0 : E =>
fun_ (fun_part f Af) -> exists v1 : E, In (couple v0 v1) (fun_part f Af))
(reunion (reunion (fun_part f Af))) v2); intros;
generalize (H0 H); clear H H0 H1; intros.
elim H; clear H; intros.
generalize (H0 (lem_fun_part_is_fun f Af)); clear H0; intros.
elim H0; clear H0; intros.
unfold fun_part in H0.
elim
(axs_comprehension
(fun x0 : E => exists y : E, x0 = couple y (fun_img_directe f Af y))
(cartesien (parties (dom f)) (parties (Img f)))
(couple v2 x)); intros; generalize (H1 H0); clear H0 H1 H2;
intros.
elim H0; clear H0; intros.
elim
(lem_cartesian_propertie (parties (dom f)) (parties (Img f)) (couple v2 x));
intros; generalize (H2 H0); clear H0 H2 H3; intros.
elim H0; clear H0; intros; elim H0; clear H0; intros; elim H0; clear H0;
intros; elim H2; clear H2; intros.
elim H1; clear H1; intros.
elim (lem_couple_propertie v2 x0 x x1); intros; generalize (H4 H3);
clear H3 H4 H5; intros.
elim H3; clear H3; intros; rewrite H3; auto with zfc.
unfold dom in |- *.
elim
(axs_comprehension
(fun v0 : E =>
fun_ (fun_part f Af) -> exists v1 : E, In (couple v0 v1) (fun_part f Af))
(reunion (reunion (fun_part f Af))) v2); intros;
apply H1; clear H0 H1; intros.
split; intros.
elim (axs_reunion (reunion (fun_part f Af)) v2); intros; apply H1;
clear H0 H1; intros.
exists (singleton v2); split; [ idtac | apply lem_x_in_sing_x ].
elim (axs_reunion (fun_part f Af) (singleton v2)); intros; apply H1;
clear H0 H1; intros.
exists (couple v2 (fun_img_directe f Af v2)); split;
[ idtac
| unfold couple in |- *;
elim
(axs_paire (singleton v2) (paire v2 (fun_img_directe f Af v2))
(singleton v2)); intros; apply H1; left; reflexivity ].
unfold fun_part in |- *.
elim
(axs_comprehension
(fun x : E => exists y : E, x = couple y (fun_img_directe f Af y))
(cartesien (parties (dom f)) (parties (Img f)))
(couple v2 (fun_img_directe f Af v2))); intros;
apply H1; clear H0 H1; intros.
split; [ idtac | exists v2; reflexivity ].
elim
(lem_cartesian_propertie (parties (dom f)) (parties (Img f))
(couple v2 (fun_img_directe f Af v2))); intros;
apply H1; clear H0 H1; intros.
exists v2; exists (fun_img_directe f Af v2); split;
[ auto with zfc | split; [ idtac | reflexivity ] ].
elim (axs_parties (Img f) (fun_img_directe f Af v2)); intros; apply H1;
clear H0 H1; intros.
unfold fun_img_directe in H0.
elim
(axs_comprehension
(fun x : E =>
In v2 (parties (dom f)) -> exists y : E, In y v2 /\ x = App f Af y)
(Img f) v3); intros; generalize (H1 H0); clear H0 H1 H2;
intros.
elim H0; clear H0; intros; auto with zfc.
exists (fun_img_directe f Af v2); unfold fun_part in |- *.
elim
(axs_comprehension
(fun x : E => exists y : E, x = couple y (fun_img_directe f Af y))
(cartesien (parties (dom f)) (parties (Img f)))
(couple v2 (fun_img_directe f Af v2))); intros;
apply H2; clear H1 H2; intros.
split; [ idtac | exists v2; reflexivity ].
elim
(lem_cartesian_propertie (parties (dom f)) (parties (Img f))
(couple v2 (fun_img_directe f Af v2))); intros;
apply H2; clear H1 H2; intros.
exists v2; exists (fun_img_directe f Af v2); split;
[ auto with zfc | split; [ idtac | reflexivity ] ].
elim (axs_parties (Img f) (fun_img_directe f Af v2)); intros; apply H2;
clear H1 H2; intros.
unfold fun_img_directe in H1.
elim
(axs_comprehension
(fun x : E =>
In v2 (parties (dom f)) -> exists y : E, In y v2 /\ x = App f Af y)
(Img f) v3); intros; generalize (H2 H1); clear H1 H2 H3;
intros.
elim H1; clear H1; intros; auto with zfc.
Qed.
(* End of proof of lem_fun_part_dom                                        *)
(* Proof of lem_fun_part_img                                               *)
intros; apply axs_extensionnalite; intros; unfold iff in |- *; split; intros.
unfold Img in H.
elim
(axs_comprehension
(fun v1 : E =>
fun_ (fun_part f Af) -> exists v0 : E, In (couple v0 v1) (fun_part f Af))
(reunion (reunion (fun_part f Af))) v2); intros;
generalize (H0 H); clear H H0 H1; intros.
elim H; clear H; intros.
generalize (H0 (lem_fun_part_is_fun f Af)); clear H0; intros; elim H0;
clear H0; intros.
unfold fun_part in H0.
elim
(axs_comprehension
(fun x0 : E => exists y : E, x0 = couple y (fun_img_directe f Af y))
(cartesien (parties (dom f)) (parties (Img f)))
(couple x v2)); intros; generalize (H1 H0); clear H0 H1 H2;
intros.
elim H0; clear H0; intros.
elim H1; clear H1; intros.
elim
(lem_cartesian_propertie (parties (dom f)) (parties (Img f)) (couple x v2));
intros; generalize (H2 H0); clear H0 H2 H3; intros.
elim H0; clear H0; intros; elim H0; clear H0; intros; elim H0; clear H0;
intros; elim H2; clear H2; intros.
elim (lem_couple_propertie x x1 v2 x2); intros; generalize (H4 H3);
clear H3 H4 H5; intros.
elim H3; clear H3; intros.
rewrite H4; auto with zfc.
unfold Img in |- *.
elim
(axs_comprehension
(fun v1 : E =>
fun_ (fun_part f Af) -> exists v0 : E, In (couple v0 v1) (fun_part f Af))
(reunion (reunion (fun_part f Af))) v2); intros;
apply H1; clear H0 H1; intros.
split; intros.
elim (axs_reunion (reunion (fun_part f Af)) v2); intros; apply H1;
clear H0 H1; intros.
exists (paire (fun_img_inverse f Af v2) v2); split;
[ idtac
| elim (axs_paire (fun_img_inverse f Af v2) v2 v2); intros; apply H1; right;
reflexivity ].
elim (axs_reunion (fun_part f Af) (paire (fun_img_inverse f Af v2) v2));
intros; apply H1; clear H0 H1; intros.
exists (couple (fun_img_inverse f Af v2) v2); split;
[ idtac
| unfold couple in |- *;
elim
(axs_paire (singleton (fun_img_inverse f Af v2))
(paire (fun_img_inverse f Af v2) v2)
(paire (fun_img_inverse f Af v2) v2)); intros;
apply H1; right; reflexivity ].
unfold fun_part in |- *.
elim
(axs_comprehension
(fun x : E => exists y : E, x = couple y (fun_img_directe f Af y))
(cartesien (parties (dom f)) (parties (Img f)))
(couple (fun_img_inverse f Af v2) v2)); intros;
apply H1; clear H0 H1; intros.
split; [ idtac | exists (fun_img_inverse f Af v2) ].
elim
(lem_cartesian_propertie (parties (dom f)) (parties (Img f))
(couple (fun_img_inverse f Af v2) v2)); intros;
apply H1; clear H0 H1; intros.
exists (fun_img_inverse f Af v2); exists v2; split;
[ idtac | split; [ auto with zfc | reflexivity ] ].
elim (axs_parties (dom f) (fun_img_inverse f Af v2)); intros; apply H1;
clear H0 H1; intros.
unfold fun_img_inverse in H0.
elim
(axs_comprehension
(fun x : E => In v2 (parties (Img f)) -> In (App f Af x) v2)
(dom f) v3); intros; generalize (H1 H0); clear H0 H1 H2;
intros.
elim H0; clear H0; intros; auto with zfc.
elim
(lem_couple_propertie (fun_img_inverse f Af v2) (fun_img_inverse f Af v2) v2
(fun_img_directe f Af (fun_img_inverse f Af v2)));
intros; apply H1; clear H0 H1; intros.
split;
[ reflexivity
| apply axs_extensionnalite; intros; unfold iff in |- *; split; intros ].
unfold fun_img_directe in |- *.
elim
(axs_comprehension
(fun x : E =>
In (fun_img_inverse f Af v2) (parties (dom f)) ->
exists y : E, In y (fun_img_inverse f Af v2) /\ x = App f Af y)
(Img f) v0); intros; apply H2; clear H1 H2; intros.
split; intros.
elim (axs_parties (Img f) v2); intros; generalize (H1 H); clear H1; intros.
exact (H1 v0 H0).
elim (axs_parties (Img f) v2); intros; generalize (H2 H); clear H2 H3; intros.
generalize (H2 v0 H0); clear H2; intros.
generalize (lem_App_rev f v0 Af H2); intros; elim H3; clear H3; intros;
elim H3; clear H3; intros.
exists x; split.
unfold fun_img_inverse in |- *.
elim
(axs_comprehension
(fun x0 : E => In v2 (parties (Img f)) -> In (App f Af x0) v2)
(dom f) x); intros; apply H6; clear H5 H6; intros.
split; [ auto with zfc | intros ].
generalize (lem_eval_propertie f x v0 Af H4); intros.
rewrite <- H6; auto with zfc.
exact (lem_eval_propertie f x v0 Af H4).
unfold fun_img_directe in H0.
elim
(axs_comprehension
(fun x : E =>
In (fun_img_inverse f Af v2) (parties (dom f)) ->
exists y : E, In y (fun_img_inverse f Af v2) /\ x = App f Af y)
(Img f) v0); intros; generalize (H1 H0); clear H0 H1 H2;
intros.
elim H0; clear H0; intros.
cut (In (fun_img_inverse f Af v2) (parties (dom f))); intros.
generalize (H1 H2); clear H1 H2; intros.
elim H1; clear H1; intros; elim H1; clear H1; intros.
unfold fun_img_inverse in H1.
elim
(axs_comprehension
(fun x0 : E => In v2 (parties (Img f)) -> In (App f Af x0) v2)
(dom f) x); intros; generalize (H3 H1); clear H1 H3 H4;
intros.
elim H1; clear H1; intros; generalize (H3 H); clear H3; intros.
rewrite H2; auto with zfc.
clear H1; elim (axs_parties (dom f) (fun_img_inverse f Af v2)); intros;
apply H2; clear H1 H2; intros.
unfold fun_img_inverse in H1.
elim
(axs_comprehension
(fun x : E => In v2 (parties (Img f)) -> In (App f Af x) v2)
(dom f) v3); intros; generalize (H2 H1); clear H1 H2 H3;
intros.
elim H1; clear H1; intros; auto with zfc.
exists (fun_img_inverse f Af v2).
unfold fun_part in |- *.
elim
(axs_comprehension
(fun x : E => exists y : E, x = couple y (fun_img_directe f Af y))
(cartesien (parties (dom f)) (parties (Img f)))
(couple (fun_img_inverse f Af v2) v2)); intros;
apply H2; clear H1 H2; intros.
split; [ idtac | exists (fun_img_inverse f Af v2) ].
elim
(lem_cartesian_propertie (parties (dom f)) (parties (Img f))
(couple (fun_img_inverse f Af v2) v2)); intros;
apply H2; clear H1 H2; intros.
exists (fun_img_inverse f Af v2); exists v2; split;
[ idtac | split; [ auto with zfc | reflexivity ] ].
elim (axs_parties (dom f) (fun_img_inverse f Af v2)); intros; apply H2;
clear H1 H2; intros.
unfold fun_img_inverse in H1.
elim
(axs_comprehension
(fun x : E => In v2 (parties (Img f)) -> In (App f Af x) v2)
(dom f) v3); intros; generalize (H2 H1); clear H1 H2 H3;
intros.
elim H1; clear H1; intros; generalize (H2 H); clear H2; intros;
auto with zfc.
elim
(lem_couple_propertie (fun_img_inverse f Af v2) (fun_img_inverse f Af v2) v2
(fun_img_directe f Af (fun_img_inverse f Af v2)));
intros; apply H2; clear H1 H2; intros.
split;
[ reflexivity
| apply axs_extensionnalite; unfold iff in |- *; split; intros ].
unfold fun_img_directe in |- *.
elim
(axs_comprehension
(fun x : E =>
In (fun_img_inverse f Af v2) (parties (dom f)) ->
exists y : E, In y (fun_img_inverse f Af v2) /\ x = App f Af y)
(Img f) v0); intros; apply H3; clear H2 H3; intros.
split; elim (axs_parties (Img f) v2); intros.
exact (H2 H v0 H1).
elim (axs_parties (Img f) v2); intros.
generalize (H5 H v0 H1); clear H5 H6; intros.
generalize (lem_App_rev f v0 Af H5); intros.
elim H6; clear H6; intros; elim H6; clear H6; intros.
exists x; split.
unfold fun_img_inverse in |- *.
elim
(axs_comprehension
(fun x0 : E => In v2 (parties (Img f)) -> In (App f Af x0) v2)
(dom f) x); intros; apply H9; clear H8 H9; intros.
split; [ auto with zfc | intros ].
generalize (lem_eval_propertie f x v0 Af H7); intros.
rewrite <- H9; auto with zfc.
exact (lem_eval_propertie f x v0 Af H7).
unfold fun_img_directe in H1.
elim
(axs_comprehension
(fun x : E =>
In (fun_img_inverse f Af v2) (parties (dom f)) ->
exists y : E, In y (fun_img_inverse f Af v2) /\ x = App f Af y)
(Img f) v0); intros; generalize (H2 H1); clear H1 H2 H3;
intros.
elim H1; clear H1; intros.
cut (In (fun_img_inverse f Af v2) (parties (dom f))); intros.
generalize (H2 H3); clear H2 H3; intros.
elim H2; clear H2; intros; elim H2; clear H2; intros.
unfold fun_img_inverse in H2.
elim
(axs_comprehension
(fun x0 : E => In v2 (parties (Img f)) -> In (App f Af x0) v2)
(dom f) x); intros; generalize (H4 H2); clear H2 H4 H5;
intros.
elim H2; clear H2; intros; generalize (H4 H); clear H4; intros.
rewrite H3; auto with zfc.
clear H2; elim (axs_parties (dom f) (fun_img_inverse f Af v2)); intros;
apply H3; clear H2 H3; intros.
unfold fun_img_inverse in H2.
elim
(axs_comprehension
(fun x : E => In v2 (parties (Img f)) -> In (App f Af x) v2)
(dom f) v3); intros; generalize (H3 H2); clear H2 H3 H4;
intros.
elim H2; clear H2; intros; auto with zfc.
Qed.
(* End of proof of lem_fun_part_img                                        *)
(* Proof of lem_fun_img_inv_is_in_pdom                                     *)
intros.
elim (axs_parties (dom f) (fun_img_inverse f Af x)); intros; apply H1;
clear H0 H1; intros.
unfold fun_img_inverse in H0.
elim
(axs_comprehension
(fun x0 : E => In x (parties (Img f)) -> In (App f Af x0) x)
(dom f) v3); intros; generalize (H1 H0); clear H0 H1 H2;
intros.
elim H0; clear H0; intros; auto with zfc.
Qed.
(* End of proof of lem_fun_img_inv_is_in_pdom                              *)
(* Proof of lem_fun_img_prop1                                              *)
intros; apply axs_extensionnalite; intros; unfold iff in |- *; split; intros.
unfold fun_img_directe in H0.
elim
(axs_comprehension
(fun x0 : E =>
In (fun_img_inverse f Af x) (parties (dom f)) ->
exists y : E, In y (fun_img_inverse f Af x) /\ x0 = App f Af y)
(Img f) v2); intros; generalize (H1 H0); clear H0 H1 H2;
intros.
elim H0; clear H0; intros.
generalize (H1 (lem_fun_img_inv_is_in_pdom f Af x H)); clear H1; intros.
elim H1; clear H1; intros.
elim H1; clear H1; intros.
unfold fun_img_inverse in H1.
elim
(axs_comprehension
(fun x1 : E => In x (parties (Img f)) -> In (App f Af x1) x)
(dom f) x0); intros; generalize (H3 H1); clear H1 H3 H4;
intros.
elim H1; clear H1; intros; generalize (H3 H); clear H3; intros.
rewrite H2; auto with zfc.
unfold fun_img_directe in |- *.
elim
(axs_comprehension
(fun x0 : E =>
In (fun_img_inverse f Af x) (parties (dom f)) ->
exists y : E, In y (fun_img_inverse f Af x) /\ x0 = App f Af y)
(Img f) v2); intros; apply H2; clear H1 H2; intros.
split; intros.
elim (axs_parties (Img f) x); intros; generalize (H1 H); clear H1 H2; intros;
auto with zfc.
elim (axs_parties (Img f) x); intros; generalize (H2 H); clear H2 H3; intros.
generalize (H2 v2 H0); clear H2; intros.
generalize (lem_App_rev f v2 Af H2); intros.
elim H3; clear H3; intros; elim H3; clear H3; intros.
exists x0; split.
unfold fun_img_inverse in |- *.
elim
(axs_comprehension
(fun x1 : E => In x (parties (Img f)) -> In (App f Af x1) x)
(dom f) x0); intros; apply H6; clear H5 H6; intros.
split; [ auto with zfc | intros; clear H5 ].
generalize (lem_eval_propertie f x0 v2 Af H4); intros.
rewrite <- H5; auto with zfc.
exact (lem_eval_propertie f x0 v2 Af H4).
Qed.
(* End of proof of lem_fun_img_prop1                                       *)
(* Proof of lem_fun_img_dir_is_in_pimg                                     *)
intros.
elim (axs_parties (Img f) (fun_img_directe f Af x)); intros; apply H1;
clear H0 H1; intros.
unfold fun_img_directe in H0.
elim
(axs_comprehension
(fun x0 : E =>
In x (parties (dom f)) -> exists y : E, In y x /\ x0 = App f Af y)
(Img f) v3); intros; generalize (H1 H0); clear H0 H1 H2;
intros.
elim H0; clear H0; intros; auto with zfc.
Qed.
(* End of proof of lem_fun_img_dir_is_in_pimg                              *)
(* Proof of lem_fun_img_prop2                                              *)
intros; unfold inc in |- *; intros.
unfold fun_img_inverse in |- *.
elim
(axs_comprehension
(fun x0 : E =>
In (fun_img_directe f Af x) (parties (Img f)) ->
In (App f Af x0) (fun_img_directe f Af x)) (dom f) v0);
intros; apply H2; clear H1 H2; intros.
split; intros.
elim (axs_parties (dom f) x); intros; generalize (H1 H); clear H H1 H2;
intros.
exact (H v0 H0).
unfold fun_img_directe in |- *.
elim
(axs_comprehension
(fun x0 : E =>
In x (parties (dom f)) -> exists y : E, In y x /\ x0 = App f Af y)
(Img f) (App f Af v0)); intros; apply H3; clear H2 H3;
intros.
split; [ idtac | intros; clear H2 ].
elim (axs_parties (dom f) x); intros; generalize (H2 H); clear H2 H3; intros.
generalize (H2 v0 H0); clear H2; intros.
generalize (lem_eval_prop2 f v0 Af H2); intros.
exact (lem_fun_and_img f v0 (App f Af v0) Af H3).
exists v0; split; [ auto with zfc | reflexivity ].
Qed.
(* End of proof of lem_fun_img_prop2                                       *)
(* Proof of lem_fun_part_eval_prop                                         *)
intros; apply axs_extensionnalite; intros; unfold iff in |- *; split; intros.
unfold App in H0.
elim
(axs_comprehension
(fun z : E => exists y : E, In (couple x y) (fun_part f Af) /\ In z y)
(reunion (Img (fun_part f Af))) v2); intros; generalize (H1 H0);
clear H0 H1 H2; intros.
elim H0; clear H0; intros; elim H1; clear H1; intros; elim H1; clear H1;
intros.
unfold fun_part in H1.
elim
(axs_comprehension
(fun x1 : E => exists y : E, x1 = couple y (fun_img_directe f Af y))
(cartesien (parties (dom f)) (parties (Img f)))
(couple x x0)); intros; generalize (H3 H1); clear H1 H3 H4;
intros.
elim H1; clear H1; intros; elim H3; clear H3; intros.
elim (lem_couple_propertie x x1 x0 (fun_img_directe f Af x1)); intros;
generalize (H4 H3); clear H3 H4 H5; intros.
elim H3; clear H3; intros; rewrite H3; rewrite <- H4; auto with zfc.
generalize H; rewrite (lem_fun_part_dom f Af); intros.
unfold fun_img_directe in H0.
elim
(axs_comprehension
(fun x0 : E =>
In x (parties (dom f)) -> exists y : E, In y x /\ x0 = App f Af y)
(Img f) v2); intros; generalize (H2 H0); clear H0 H2 H3;
intros.
elim H0; clear H0; intros; generalize (H2 H1); clear H2; intros.
elim H2; clear H2; intros; elim H2; clear H2; intros.
unfold App in |- *.
elim
(axs_comprehension
(fun z : E => exists y : E, In (couple x y) (fun_part f Af) /\ In z y)
(reunion (Img (fun_part f Af))) v2); intros; apply H5;
clear H4 H5; intros.
split.
rewrite (lem_fun_part_img f Af).
rewrite (lem_reunion_parties (Img f)).
auto with zfc.
generalize (lem_fun_part_is_fun f Af); intros.
generalize (lem_App (fun_part f Af) x H4 H); intros.
elim H5; clear H5; intros; elim H5; clear H5; intros.
exists x1; split; [ auto with zfc | idtac ].
unfold fun_part in H6.
elim
(axs_comprehension
(fun x0 : E => exists y : E, x0 = couple y (fun_img_directe f Af y))
(cartesien (parties (dom f)) (parties (Img f)))
(couple x x1)); intros; generalize (H7 H6); clear H6 H7 H8;
intros.
elim H6; clear H6; intros; elim H7; clear H7; intros.
elim (lem_couple_propertie x x2 x1 (fun_img_directe f Af x2)); intros;
generalize (H8 H7); clear H7 H8 H9; intros.
elim H7; clear H7; intros.
rewrite H8; rewrite <- H7.
unfold fun_img_directe in |- *.
elim
(axs_comprehension
(fun x0 : E =>
In x (parties (dom f)) -> exists y : E, In y x /\ x0 = App f Af y)
(Img f) v2); intros; apply H10; clear H9 H10; intros.
split; [ auto with zfc | intros; exists x0; split; auto with zfc ].
Qed.
(* End of proof of lem_fun_part_eval_prop                                  *)
(***************************************************************************)
(***************************************************************************)
(* Reciproque: application des parties de l'image de f dans les parties du *)
(* domaine de f                                                            *)
(***************************************************************************)
(***************************************************************************)
Definition fun_part_inv (f : E) (Af : fun_ f) :=
subset (fun x : E => exists y : E, x = couple y (fun_img_inverse f Af y))
(cartesien (parties (Img f)) (parties (dom f))).
(* Proof of lem_fun_part_inv_is_fun                                        *)
intros; unfold fun_ in |- *; split; intros.
exists (parties (Img f)); exists (parties (dom f)); unfold inc in |- *;
intros.
unfold fun_part_inv in H.
elim
(axs_comprehension
(fun x : E => exists y : E, x = couple y (fun_img_inverse f Af y))
(cartesien (parties (Img f)) (parties (dom f))) v0);
intros; generalize (H0 H); clear H H0 H1; intros.
elim H; clear H; intros; auto with zfc.
unfold fun_part_inv in H; unfold fun_part_inv in H0.
elim
(axs_comprehension
(fun x0 : E => exists y0 : E, x0 = couple y0 (fun_img_inverse f Af y0))
(cartesien (parties (Img f)) (parties (dom f)))
(couple x y)); intros; generalize (H1 H); clear H H1 H2;
intros.
elim
(axs_comprehension
(fun x0 : E => exists y : E, x0 = couple y (fun_img_inverse f Af y))
(cartesien (parties (Img f)) (parties (dom f)))
(couple x z)); intros; generalize (H1 H0); clear H0 H1 H2;
intros.
elim H; clear H; intros; elim H1; clear H1; intros.
elim H0; clear H0; intros; elim H2; clear H2; intros.
elim (lem_couple_propertie x x0 y (fun_img_inverse f Af x0)); intros;
generalize (H3 H1); clear H1 H3 H4; intros.
elim (lem_couple_propertie x x1 z (fun_img_inverse f Af x1)); intros;
generalize (H3 H2); clear H2 H3 H4; intros.
elim H1; clear H1; intros; elim H2; clear H2; intros.
rewrite H3; rewrite H4; rewrite <- H1; rewrite <- H2; reflexivity.
Qed.
(* End of proof of lem_fun_part_inv_is_fun                                 *)
(* Proof of lem_fun_part_inv_dom                                           *)
intros; apply axs_extensionnalite; intros; unfold iff in |- *; split; intros.
unfold dom in H.
elim
(axs_comprehension
(fun v0 : E =>
fun_ (fun_part_inv f Af) ->
exists v1 : E, In (couple v0 v1) (fun_part_inv f Af))
(reunion (reunion (fun_part_inv f Af))) v2); intros;
generalize (H0 H); clear H H0 H1; intros.
elim H; clear H; intros.
generalize (H0 (lem_fun_part_inv_is_fun f Af)); clear H0; intros.
elim H0; clear H0; intros.
unfold fun_part_inv in H0.
elim
(axs_comprehension
(fun x0 : E => exists y : E, x0 = couple y (fun_img_inverse f Af y))
(cartesien (parties (Img f)) (parties (dom f)))
(couple v2 x)); intros; generalize (H1 H0); clear H0 H1 H2;
intros.
elim H0; clear H0; intros; elim H1; clear H1; intros.
elim
(lem_cartesian_propertie (parties (Img f)) (parties (dom f)) (couple v2 x));
intros; generalize (H2 H0); clear H0 H2 H3; intros.
elim H0; clear H0; intros; elim H0; clear H0; intros; elim H0; clear H0;
intros; elim H2; clear H2; intros.
elim (lem_couple_propertie v2 x1 x x2); intros; generalize (H4 H3);
clear H3 H4 H5; intros.
elim H3; clear H3; intros.
rewrite H3; auto with zfc.
elim (axs_parties (Img f) v2); intros; generalize (H0 H); clear H0 H1; intros.
unfold dom in |- *.
elim
(axs_comprehension
(fun v0 : E =>
fun_ (fun_part_inv f Af) ->
exists v1 : E, In (couple v0 v1) (fun_part_inv f Af))
(reunion (reunion (fun_part_inv f Af))) v2); intros;
apply H2; clear H1 H2; intros.
split; intros.
elim (axs_reunion (reunion (fun_part_inv f Af)) v2); intros; apply H2;
clear H1 H2; intros.
exists (paire v2 (fun_img_inverse f Af v2)).
split;
[ idtac
| elim (axs_paire v2 (fun_img_inverse f Af v2) v2); intros; apply H2; left;
reflexivity ].
elim (axs_reunion (fun_part_inv f Af) (paire v2 (fun_img_inverse f Af v2)));
intros; apply H2; clear H1 H2; intros.
exists (couple v2 (fun_img_inverse f Af v2)).
split;
[ idtac
| unfold couple in |- *;
elim
(axs_paire (singleton v2) (paire v2 (fun_img_inverse f Af v2))
(paire v2 (fun_img_inverse f Af v2))); intros;
apply H2; right; reflexivity ].
unfold fun_part_inv in |- *.
elim
(axs_comprehension
(fun x : E => exists y : E, x = couple y (fun_img_inverse f Af y))
(cartesien (parties (Img f)) (parties (dom f)))
(couple v2 (fun_img_inverse f Af v2))); intros;
apply H2; clear H1 H2; intros.
split; [ idtac | exists v2; auto with zfc ].
elim
(lem_cartesian_propertie (parties (Img f)) (parties (dom f))
(couple v2 (fun_img_inverse f Af v2))); intros;
apply H2; clear H1 H2; intros.
exists v2; exists (fun_img_inverse f Af v2); split;
[ auto with zfc | split; [ idtac | reflexivity ] ].
elim (axs_parties (dom f) (fun_img_inverse f Af v2)); intros; apply H2;
clear H1 H2; intros.
unfold fun_img_inverse in H1.
elim
(axs_comprehension
(fun x : E => In v2 (parties (Img f)) -> In (App f Af x) v2)
(dom f) v3); intros; generalize (H2 H1); clear H1 H2 H3;
intros.
elim H1; clear H1; intros; auto with zfc.
exists (fun_img_inverse f Af v2); unfold fun_part_inv in |- *.
elim
(axs_comprehension
(fun x : E => exists y : E, x = couple y (fun_img_inverse f Af y))
(cartesien (parties (Img f)) (parties (dom f)))
(couple v2 (fun_img_inverse f Af v2))); intros;
apply H3; clear H2 H3; intros.
split; [ idtac | exists v2; reflexivity ].
elim
(lem_cartesian_propertie (parties (Img f)) (parties (dom f))
(couple v2 (fun_img_inverse f Af v2))); intros;
apply H3; clear H2 H3; intros.
exists v2; exists (fun_img_inverse f Af v2); split;
[ auto with zfc | split; [ idtac | reflexivity ] ].
elim (axs_parties (dom f) (fun_img_inverse f Af v2)); intros; apply H3;
clear H2 H3; intros.
unfold fun_img_inverse in H2.
elim
(axs_comprehension
(fun x : E => In v2 (parties (Img f)) -> In (App f Af x) v2)
(dom f) v3); intros; generalize (H3 H2); clear H2 H3 H4;
intros.
elim H2; clear H2; intros; auto with zfc.
Qed.
(* End of proof of lem_fun_part_inv_dom                                    *)
(* Proof of lem_fun_part_inv_img                                           *)
intros; unfold inc in |- *; intros.
unfold Img in H.
elim
(axs_comprehension
(fun v1 : E =>
fun_ (fun_part_inv f Af) ->
exists v2 : E, In (couple v2 v1) (fun_part_inv f Af))
(reunion (reunion (fun_part_inv f Af))) v0); intros;
generalize (H0 H); clear H H0 H1; intros.
elim H; clear H; intros.
generalize (H0 (lem_fun_part_inv_is_fun f Af)); clear H0; intros.
elim H0; clear H0; intros.
unfold fun_part_inv in H0.
elim
(axs_comprehension
(fun x0 : E => exists y : E, x0 = couple y (fun_img_inverse f Af y))
(cartesien (parties (Img f)) (parties (dom f)))
(couple x v0)); intros; generalize (H1 H0); clear H0 H1 H2;
intros.
elim H0; clear H0; intros; elim H1; clear H1; intros.
elim
(lem_cartesian_propertie (parties (Img f)) (parties (dom f)) (couple x v0));
intros; generalize (H2 H0); clear H0 H2 H3; intros.
elim H0; clear H0; intros; elim H0; clear H0; intros; elim H0; clear H0;
intros; elim H2; clear H2; intros.
elim (lem_couple_propertie x x1 v0 x2); intros; generalize (H4 H3);
clear H3 H4 H5; intros.
elim H3; clear H3; intros.
rewrite H4; auto with zfc.
Qed.
(* End of proof of lem_fun_part_inv_img                                    *)
(* Proof of lem_fun_part_inv_eval_prop                                     *)
intros; apply axs_extensionnalite; intros; unfold iff in |- *; split; intros.
unfold App in H0.
elim
(axs_comprehension
(fun z : E => exists y : E, In (couple x y) (fun_part_inv f Af) /\ In z y)
(reunion (Img (fun_part_inv f Af))) v2); intros;
generalize (H1 H0); clear H0 H1 H2; intros.
elim H0; clear H0; intros; elim H1; clear H1; intros; elim H1; clear H1;
intros.
unfold fun_part_inv in H1.
elim
(axs_comprehension
(fun x1 : E => exists y : E, x1 = couple y (fun_img_inverse f Af y))
(cartesien (parties (Img f)) (parties (dom f)))
(couple x x0)); intros; generalize (H3 H1); clear H1 H3 H4;
intros.
elim H1; clear H1; intros; elim H3; clear H3; intros.
elim (lem_couple_propertie x x1 x0 (fun_img_inverse f Af x1)); intros;
generalize (H4 H3); clear H3 H4 H5; intros.
elim H3; clear H3; intros.
rewrite H3; rewrite <- H4; auto with zfc.
unfold fun_img_inverse in H0.
elim
(axs_comprehension
(fun x0 : E => In x (parties (Img f)) -> In (App f Af x0) x)
(dom f) v2); intros; generalize (H1 H0); clear H0 H1 H2;
intros.
elim H0; clear H0; intros.
generalize H; rewrite (lem_fun_part_inv_dom f Af); intros.
generalize (H1 H2); clear H1 H2; intros.
unfold App in |- *.
elim
(axs_comprehension
(fun z : E => exists y : E, In (couple x y) (fun_part_inv f Af) /\ In z y)
(reunion (Img (fun_part_inv f Af))) v2); intros;
apply H3; clear H2 H3; intros.
generalize (lem_fun_part_inv_is_fun f Af); intros.
elim (lem_App (fun_part_inv f Af) x H2 H); intros.
elim H3; clear H3; intros.
split.
elim (axs_reunion (Img (fun_part_inv f Af)) v2); intros; apply H6;
clear H5 H6; intros.
exists x0.
split; [ auto with zfc | idtac ].
unfold fun_part_inv in H4.
elim
(axs_comprehension
(fun x1 : E => exists y : E, x1 = couple y (fun_img_inverse f Af y))
(cartesien (parties (Img f)) (parties (dom f)))
(couple x x0)); intros; generalize (H5 H4); clear H4 H5 H6;
intros.
elim H4; clear H4; intros; elim H5; clear H5; intros.
elim (lem_couple_propertie x x1 x0 (fun_img_inverse f Af x1)); intros;
generalize (H6 H5); clear H5 H6 H7; intros.
elim H5; clear H5; intros.
rewrite H6; rewrite <- H5; clear H5 H6.
unfold fun_img_inverse in |- *.
elim
(axs_comprehension
(fun x0 : E => In x (parties (Img f)) -> In (App f Af x0) x)
(dom f) v2); intros; apply H6; clear H5 H6; intros.
split; intros; auto with zfc.
exists x0; split; [ auto with zfc | idtac ].
unfold fun_part_inv in H4.
elim
(axs_comprehension
(fun x1 : E => exists y : E, x1 = couple y (fun_img_inverse f Af y))
(cartesien (parties (Img f)) (parties (dom f)))
(couple x x0)); intros; generalize (H5 H4); clear H4 H5 H6;
intros.
elim H4; clear H4; intros; elim H5; clear H5; intros.
elim (lem_couple_propertie x x1 x0 (fun_img_inverse f Af x1)); intros;
generalize (H6 H5); clear H5 H6 H7; intros.
elim H5; clear H5; intros.
rewrite H6; rewrite <- H5; clear H5 H6.
unfold fun_img_inverse in |- *.
elim
(axs_comprehension
(fun x0 : E => In x (parties (Img f)) -> In (App f Af x0) x)
(dom f) v2); intros; apply H6; clear H5 H6; intros.
split; intros; auto with zfc.
Qed.
(* End of proof of lem_fun_part_inv_eval_prop                              *)
(***************************************************************************)
(***************************************************************************)
(* Relation inverse d'une application et applications au cas des bijections*)
(***************************************************************************)
(***************************************************************************)
(***************************************************************************)
(* On peut definir la relation inverse d'une application                   *)
(***************************************************************************)
Definition fun_recip (f : E) (Af : fun_ f) :=
subset
(fun c : E =>
exists x : E, (exists y : E, In (couple x y) f /\ c = couple y x))
(cartesien (Img f) (dom f)).
(* Proof of lem_fun_recip_is_fun_under_inj                                 *)
intros; unfold iff in |- *; split; intros.
unfold fun_inj in H.
elim H; clear H; intros; elim H0; clear H0; intros; clear H0; elim H1;
clear H1; intros; clear H0.
unfold fun_ in |- *; split; intros.
exists (Img f); exists (dom f); unfold inc in |- *; intros.
unfold fun_recip in H0.
elim
(axs_comprehension
(fun c : E =>
exists x : E, (exists y : E, In (couple x y) f /\ c = couple y x))
(cartesien (Img f) (dom f)) v0); intros; generalize (H2 H0);
clear H0 H2 H3; intros.
elim H0; clear H0; intros; auto with zfc.
unfold fun_recip in H0; unfold fun_recip in H2.
elim
(axs_comprehension
(fun c : E =>
exists x0 : E, (exists y0 : E, In (couple x0 y0) f /\ c = couple y0 x0))
(cartesien (Img f) (dom f)) (couple x y)); intros;
generalize (H3 H0); clear H0 H3 H4; intros.
elim
(axs_comprehension
(fun c : E =>
exists x0 : E, (exists y : E, In (couple x0 y) f /\ c = couple y x0))
(cartesien (Img f) (dom f)) (couple x z)); intros;
generalize (H3 H2); clear H2 H3 H4; intros.
elim H0; clear H0; intros; elim H3; clear H3; intros; elim H3; clear H3;
intros; elim H3; clear H3; intros.
elim H2; clear H2; intros; elim H5; clear H5; intros; elim H5; clear H5;
intros; elim H5; clear H5; intros.
elim (lem_couple_propertie x x1 y x0); intros; generalize (H7 H4);
clear H4 H7 H8; intros; elim H4; clear H4; intros.
generalize H3; rewrite <- H4; rewrite <- H7; clear H3 H4 H7; intros.
elim (lem_couple_propertie x x3 z x2); intros; generalize (H4 H6);
clear H4 H6 H7; intros; elim H4; clear H4; intros.
generalize H5; rewrite <- H4; rewrite <- H6; clear H4 H5 H6; intros.
generalize (lem_fun_and_img f y x Af H3); intros.
generalize (H1 x H4); unfold exUniq in |- *; intros.
elim H6; clear H6; intros; elim H6; clear H6; intros;
generalize (H7 y H3) (H7 z H5); intros.
rewrite <- H8; rewrite <- H9; reflexivity.
elim H; clear H; intros.
elim H; clear H; intros; elim H; clear H; intros.
unfold fun_inj in |- *.
split;
[ auto with zfc
| split;
[ reflexivity
| split;
[ unfold inc in |- *; intros; auto with zfc
| unfold exUniq in |- *; intros ] ] ].
generalize (lem_App_rev f b Af H1); intros; elim H2; clear H2; intros;
elim H2; clear H2; intros.
exists x1; split; [ auto with zfc | intros ].
generalize (lem_fun_and_dom f y b Af H4); intros.
cut (In (couple b x1) (fun_recip f Af)); intros.
cut (In (couple b y) (fun_recip f Af)); intros.
exact (H0 b x1 y H6 H7).
unfold fun_recip in |- *.
elim
(axs_comprehension
(fun c : E =>
exists x : E, (exists y0 : E, In (couple x y0) f /\ c = couple y0 x))
(cartesien (Img f) (dom f)) (couple b y)); intros;
apply H8; clear H7 H8; intros.
split;
[ idtac | exists y; exists b; split; [ auto with zfc | reflexivity ] ].
elim (lem_cartesian_propertie (Img f) (dom f) (couple b y)); intros; apply H8;
clear H7 H8; intros.
exists b; exists y; split;
[ auto with zfc | split; [ auto with zfc | reflexivity ] ].
unfold fun_recip in |- *.
elim
(axs_comprehension
(fun c : E =>
exists x : E, (exists y : E, In (couple x y) f /\ c = couple y x))
(cartesien (Img f) (dom f)) (couple b x1)); intros;
apply H7; clear H6 H7; intros.
split;
[ idtac | exists x1; exists b; split; [ auto with zfc | reflexivity ] ].
elim (lem_cartesian_propertie (Img f) (dom f) (couple b x1)); intros;
apply H7; clear H6 H7; intros.
exists b; exists x1; split;
[ auto with zfc | split; [ auto with zfc | reflexivity ] ].
Qed.
(* End of proof of lem_fun_recip_is_fun_under_inj                          *)
(* Proof of lem_xyinf_yxinrecipf                                           *)
intros; unfold fun_recip in |- *.
elim
(axs_comprehension
(fun c : E =>
exists x0 : E, (exists y0 : E, In (couple x0 y0) f /\ c = couple y0 x0))
(cartesien (Img f) (dom f)) (couple y x)); intros;
apply H1; clear H0 H1; intros.
split;
[ idtac | exists x; exists y; split; [ auto with zfc | reflexivity ] ].
generalize (lem_fun_and_dom f x y Af H); intros.
generalize (lem_fun_and_img f x y Af H); intros.
elim (lem_cartesian_propertie (Img f) (dom f) (couple y x)); intros; apply H3;
clear H2 H3; intros.
exists y; exists x; split;
[ auto with zfc | split; [ auto with zfc | reflexivity ] ].
Qed.
(* End of proof of lem_xyinf_yxinrecipf                                    *)
(* Proof of lem_fun_recip_is_bij_under_bij                                 *)
intros.
generalize (lem_bij_is_inj f (dom f) (Img f) H); intros.
elim (lem_fun_recip_is_fun_under_inj f Af); intros; generalize (H1 H0);
clear H0 H1 H2; intros.
unfold fun_bij in H.
elim H; clear H; intros; clear H; elim H1; clear H1; intros; clear H; elim H1;
clear H1; intros; clear H.
unfold fun_bij in |- *.
split; [ auto with zfc | split ].
apply axs_extensionnalite; unfold iff in |- *; split; intros.
unfold dom in H.
elim
(axs_comprehension
(fun v0 : E =>
fun_ (fun_recip f Af) ->
exists v1 : E, In (couple v0 v1) (fun_recip f Af))
(reunion (reunion (fun_recip f Af))) v2); intros;
generalize (H2 H); clear H H2 H3; intros.
elim H; clear H; intros; generalize (H2 H0); clear H2; intros; elim H2;
clear H2; intros.
unfold fun_recip in H2.
elim
(axs_comprehension
(fun c : E =>
exists x0 : E, (exists y : E, In (couple x0 y) f /\ c = couple y x0))
(cartesien (Img f) (dom f)) (couple v2 x)); intros;
generalize (H3 H2); clear H2 H3 H4; intros.
elim H2; clear H2; intros.
elim (lem_cartesian_propertie (Img f) (dom f) (couple v2 x)); intros;
generalize (H4 H2); clear H2 H4 H5; intros.
elim H2; clear H2; intros; elim H2; clear H2; intros; elim H2; clear H2;
intros; elim H4; clear H4; intros.
elim (lem_couple_propertie v2 x0 x x1); intros; generalize (H6 H5);
clear H5 H6 H7; intros.
elim H5; clear H5; intros.
rewrite H5; auto with zfc.
generalize (H1 v2 H); intros.
unfold exUniq in H2.
elim H2; clear H2; intros; elim H2; clear H2; intros.
generalize (lem_xyinf_yxinrecipf f Af x v2 H2); intros.
exact (lem_fun_and_dom (fun_recip f Af) v2 x H0 H4).
split.
apply axs_extensionnalite; unfold iff in |- *; split; intros.
unfold Img in H.
elim
(axs_comprehension
(fun v1 : E =>
fun_ (fun_recip f Af) ->
exists v0 : E, In (couple v0 v1) (fun_recip f Af))
(reunion (reunion (fun_recip f Af))) v2); intros;
generalize (H2 H); clear H H2 H3; intros.
elim H; clear H; intros; generalize (H2 H0); clear H2; intros; elim H2;
clear H2; intros.
unfold fun_recip in H2.
elim
(axs_comprehension
(fun c : E =>
exists x0 : E, (exists y : E, In (couple x0 y) f /\ c = couple y x0))
(cartesien (Img f) (dom f)) (couple x v2)); intros;
generalize (H3 H2); clear H2 H3 H4; intros.
elim H2; clear H2; intros.
elim (lem_cartesian_propertie (Img f) (dom f) (couple x v2)); intros;
generalize (H4 H2); clear H2 H4 H5; intros.
elim H2; clear H2; intros; elim H2; clear H2; intros; elim H2; clear H2;
intros; elim H4; clear H4; intros.
elim (lem_couple_propertie x x0 v2 x1); intros; generalize (H6 H5);
clear H5 H6 H7; intros.
elim H5; clear H5; intros; rewrite H6; auto with zfc.
generalize (lem_App f v2 Af H); intros.
elim H2; clear H2; intros; elim H2; clear H2; intros.
generalize (lem_xyinf_yxinrecipf f Af v2 x H3); intros.
exact (lem_fun_and_img (fun_recip f Af) x v2 H0 H4).
intros.
unfold exUniq in |- *; intros.
unfold Img in H.
elim
(axs_comprehension
(fun v1 : E =>
fun_ (fun_recip f Af) ->
exists v0 : E, In (couple v0 v1) (fun_recip f Af))
(reunion (reunion (fun_recip f Af))) b); intros;
generalize (H2 H); clear H H2 H3; intros.
elim H; clear H; intros; generalize (H2 H0); clear H2; intros; elim H2;
clear H2; intros.
exists x; split; [ auto with zfc | intros ].
unfold fun_recip in H2; unfold fun_recip in H3.
elim
(axs_comprehension
(fun c : E =>
exists x0 : E, (exists y : E, In (couple x0 y) f /\ c = couple y x0))
(cartesien (Img f) (dom f)) (couple x b)); intros;
generalize (H4 H2); clear H2 H4 H5; intros.
elim
(axs_comprehension
(fun c : E =>
exists x : E, (exists y0 : E, In (couple x y0) f /\ c = couple y0 x))
(cartesien (Img f) (dom f)) (couple y b)); intros;
generalize (H4 H3); clear H3 H4 H5; intros.
elim H2; clear H2; intros; elim H4; clear H4; intros; elim H4; clear H4;
intros; elim H4; clear H4; intros.
elim H3; clear H3; intros; elim H6; clear H6; intros; elim H6; clear H6;
intros; elim H6; clear H6; intros.
elim (lem_couple_propertie x x1 b x0); intros; generalize (H8 H5);
clear H5 H8 H9; intros; elim H5; clear H5; intros.
elim (lem_couple_propertie y x3 b x2); intros; generalize (H9 H7);
clear H7 H9 H10; intros; elim H7; clear H7; intros.
generalize H4 H6; clear H4 H6; rewrite <- H8; rewrite <- H9; rewrite <- H5;
rewrite <- H7; clear H5 H7 H8 H9; intros.
generalize Af; intros.
elim Af0; clear Af0; intros.
exact (H7 b x y H4 H6).
Qed.
(* End of proof of lem_fun_recip_is_bij_under_bij                          *)

(***************************************************************************)
(* Si f est une injection de (dom f) dans (Img f) alors c'est une          *)
(* bijection de (dom f) dans (Img f)                                       *)
(***************************************************************************)
Lemma lem_fun_inj_dom_img_is_bij :
forall (f : E) (Af : fun_ f),
fun_inj f (dom f) (Img f) -> fun_bij f (dom f) (Img f).