proposition: Lemma gacent1 : 'C_(|to)(1) = R.
proof: Proof. by rewrite /gacent (setIidPr (sub1G _)) afix1 setIT. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)