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