proposition: Lemma actmEfun a : a \in D -> actm to a = to^~ a.
proof: Proof. by rewrite /actm => ->. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)