proposition: Lemma quotm_ker_proof : 'ker (coset H) \subset 'ker fH_G.
proof: Proof. by rewrite ker_restrm ker_comp !ker_coset morphpreIdom morphimK ?mulG_subr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq div) mathcomp(choice fintype prime finset fingroup morphism) mathcomp(automorphism)