intros.
unfold fun_d_dstar in H0.
cut
(dans (couple e0 (couple epsilon e)) d \/
dans (couple e0 (couple epsilon e)) (delta g0 qa));
auto.
intro Ht; elim Ht; clear Ht.
intro.
cut (inclus d (prodcart q (prodcart alph q))).
2: apply automate_def1 with (singleton g0) qa; assumption.
intro.
cut (dans (couple e0 (couple epsilon e)) (prodcart q (prodcart alph q))).
2: apply dans_trans with d; auto.
intro.
cut (dans e0 q /\ dans (couple epsilon e) (prodcart alph q)).
2: apply coupl2; auto.
intro Ht; elim Ht; clear Ht; intros.
cut (dans epsilon alph /\ dans e q).
2: apply coupl2; auto.
intro Ht; elim Ht; clear Ht; intros.
absurd (dans epsilon alph); auto.
red in |- *; intro; apply not_dans_epsilon_alph; assumption.
unfold delta in |- *.
intro.
cut
(exists y : Elt,
dans y qa /\ couple e0 (couple epsilon e) = transition_back g0 y :>Elt).
2: apply dans_map; auto.
intro Ht; elim Ht; clear Ht; intros y Ht; elim Ht; clear Ht; intros.
unfold transition_back in H3.
cut (e0 = y :>Elt /\ couple epsilon e = couple epsilon g0 :>Elt).
2: apply equal_couple; auto.
intro Ht; elim Ht; clear Ht; intros.
cut (epsilon = epsilon :>Elt /\ e = g0 :>Elt).
2: apply equal_couple; auto.
intro Ht; elim Ht; clear Ht; intros.
rewrite H4.
auto.
Qed.
(*									*)
(*  Si on a un chemin de g0 a g0 dans A alors c'est par le mot nil.	*)
(*									*)

(* Specifications: *)
Lemma chemin_g0_g0 :
forall (q qa d : Ensf) (g0 : Elt) (w0 : Word),
automate q (singleton g0) qa d ->
(forall e x : Elt, dans (couple g0 (couple x e)) d -> x = epsilon :>Elt) ->
chemin g0 g0 q d w0 -> w0 = nil :>Word.