proposition: Lemma preim_permV s S : s^-1 @^-1: S = s @: S.
proof: Proof. by rewrite -im_permV invgK. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finfun bigop finset binomial) mathcomp(fingroup morphism)