proposition: Lemma lcosetM A x y : (x * y) *: A = x *: (y *: A).
proof: Proof. by rewrite -mulg_set1 mulgA. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)