proposition: Lemma dprod_normal2 A B G : A \x B = G -> A <| G /\ B <| G.
proof: Proof. by move/dprodWcp/cprod_normal2. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(choice fintype bigop finset fingroup morphism) mathcomp(quotient action)