proposition: Lemma weak_second_isog : H / (K :&: H) \isog H * K / K.
proof: Proof. by rewrite quotientMidr; apply: second_isog. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq div) mathcomp(choice fintype prime finset fingroup morphism) mathcomp(automorphism)