proposition: Lemma actM x a b : to x (a * b) = to (to x a) b.
proof: Proof. by rewrite actMin ?inE. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)