unfold X2', V2', R2', S2', GGG2, GG2, G2 in |- *.
apply image_isGram.
auto.
change (Mots X2') in |- *.
rewrite egal_X_X2'.
auto.
apply inter_Xim_Vim_empty; auto.
Qed.
Hint Resolve Grammaire2'.

Lemma inter_V1'_V2'_empty : inter V1' V2' empty.
unfold V1', V2' in |- *; simpl in |- *.