proposition: Lemma xcprodmEl : {in H, forall x, xcprodm (cpairg1 x) = fH x}.
proof: Proof. by move=> x Hx; rewrite /xcprodm cprodmEl ?mem_morphim ?ifactmE. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient action gproduct gfunctor) mathcomp(cyclic)