proposition: Lemma Frobenius_autM_comm x y : comm x y -> (x * y)^f = x^f * y^f.
proof: Proof. exact: exprMn_comm. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)