proposition: Lemma im_xcprodml A : xcprodm @* (cpairg1 @* A) = fH @* A.
proof: Proof. rewrite -!(morphimIdom _ A) morphim_cprodml ?morphimS ?subsetIl //. by rewrite morphim_ifactm ?subsetIl. 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)