simple induction E1; intros A1 f1 r1; simple induction E2; intros A2 f2 r2.
intros E1' E2' i1 i2.
elim (IN_EXType (sup A1 f1) E1').
intros x e1; simpl in x.
elim (IN_EXType (sup A2 f2) E2').
intros x0 e2; simpl in x.
apply IN_sound_left with (Couple (pi2 (sup A1 f1) x) (pi2 (sup A2 f2) x0));
auto with zfc.
apply EQ_tran with (Couple (pi2 (sup A1 f1) x) E2'); auto with zfc.
apply Couple_sound_right.
auto with zfc.
apply Couple_sound_left; auto with zfc.
simpl in |- *.
simpl in |- *.
exists (pair_t _ _ x x0).
simpl in |- *.
split.
simple induction x1; simpl in |- *.
exists true; simpl in |- *.
split.
simple induction x2; simpl in |- *.
exists true; auto with zfc.
exists true; auto with zfc.
simple induction y; exists true; auto with zfc.
exists false; simpl in |- *.
split.
simple induction x2.
exists true; simpl in |- *; auto with zfc.
split.
simple induction x3.
simple induction y.
exists false; auto with zfc.
simple induction y; simpl in |- *.
exists true; auto with zfc.
exists false; auto with zfc.
simple induction y; simpl in |- *.
exists true; auto with zfc.
exists false; auto with zfc.
auto with zfc.
auto with zfc.
Qed.

Theorem Couple_Prod_IN :
forall E1 E2 E1' E2' : Ens,
IN (Couple E1' E2') (Prod E1 E2) -> IN E1' E1 /\ IN E2' E2.