simple induction 1; intros e1 e2.
apply INC_EQ; unfold INC in |- *.
change
(forall E : Ens,
IN E (Union (sup A1 (fun a1 : A1 => Power (Vee (f1 a1))))) ->
IN E (Union (sup A2 (fun a2 : A2 => Power (Vee (f2 a2))))))
in |- *.
intros E i.
apply
IN_sound_right with (Union (sup A1 (fun a1 : A1 => Power (Vee (f1 a1)))));
try trivial with zfc.
apply Union_sound.
split.
intros a1; elim (e1 a1).
intros a2 h.
exists a2.
apply Power_sound.
apply HR1.
assumption.
intros a2; elim (e2 a2); intros a1 h; exists a1; apply Power_sound;
auto with zfc.
change
(forall E : Ens,
IN E (Union (sup A2 (fun a2 : A2 => Power (Vee (f2 a2))))) ->
IN E (Union (sup A1 (fun a1 : A1 => Power (Vee (f1 a1))))))
in |- *.
intros E i.
apply
IN_sound_right with (Union (sup A2 (fun a2 : A2 => Power (Vee (f2 a2))))).
apply Union_sound.
split.
intros a2; elim (e2 a2); intros a1 h; exists a1.
apply Power_sound; auto with zfc.
intros a1; elim (e1 a1); intros a2 h; exists a2.
apply Power_sound; auto with zfc.
assumption.
Qed.

(* Specifications: *)
Lemma IN_Vee :
forall V W : Ens, IN W V -> forall E : Ens, INC E (Vee W) -> IN E (Vee V).