proposition: Lemma sdprod_isog G A B : A ><| B = G -> B \isog G / A.
proof: Proof. by case/sdprod_isom=> nAB; apply: isom_isog. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(choice fintype bigop finset fingroup morphism) mathcomp(quotient action)