proposition: Lemma morphim_quotm A : quotm @* (A / H) = f @* A / f @* H.
proof: Proof. by rewrite morphim_factm morphim_restrm morphim_comp morphimIdom. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq div) mathcomp(choice fintype prime finset fingroup morphism) mathcomp(automorphism)