proposition: Lemma gacentD1 A : 'C_(|to)(A^#) = 'C_(|to)(A).
proof: Proof. rewrite -gacentIdom -gacent_gen ?subsetIl // setIDA genD1 ?group1 //. by rewrite gacent_gen ?subsetIl // gacentIdom. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)