(* Proof of lem_inter_unicite                                              *)
intros; apply axs_extensionnalite; intros.
elim (H v2); clear H; intros.
elim (lem_inter_propertie a b v2); intros; split; intros; auto with zfc.
Qed.
(* End of proof of lem_inter_unicite                                       *)

Lemma lem_inter_vide_prop : forall x : E, inter x Vide = Vide.
intros; unfold inter in |- *; apply axs_extensionnalite; intros;
unfold iff in |- *; split; intros.