proposition: Lemma afix1 : 'Fix_to(1) = setT.
proof: Proof. by apply/setP=> x; rewrite !inE sub1set inE act1 eqxx. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)