proposition: Lemma gacent1E : 'C_(|to)[a] = 'Fix_(R | to)[a].
proof: Proof. by rewrite /gacent [D :&: _](setIidPr _) ?sub1set. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)