proposition: Lemma sub_afixRs_norm G x : (G :* x \in 'Fix_('Rs)(G)) = (x \in 'N(G)).
proof: Proof. by rewrite sub_afixRs_norms -groupV inE sub_conjgV. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)