proposition: Lemma gacentIim : 'C_(R | to)(A) = 'C_(|to)(A).
proof: Proof. by rewrite setIA setIid. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)