proposition: Lemma classGidr x : {in G, normalised (x ^: G)}.
proof: Proof. by move=> y Gy /=; rewrite -class_rcoset rcoset_id. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)