intro G2.
unfold Vu in |- *.
unfold C in |- *.
unfold Gunion in |- *.
simpl in |- *.
apply union_inter.
apply isGram2 with R1 S1; assumption.
apply isGram2 with R2 S2; assumption.
Qed.

Lemma Gunion_Regles :
isGram X V1 R1 S1 -> isGram X V2 R2 S2 -> Regles X Vu Ru.