proposition: Lemma setactVin S a : a \in D -> to^* S a^-1 = to^~ a @^-1: S.
proof: Proof. by move=> Da; apply: can2_imset_pre; [apply: actKVin | apply: actKin]. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)