proposition: Lemma rcoset_is_action : is_action setT (@rcoset gT).
proof: Proof. by apply: is_total_action => [A|A x y]; rewrite !rcosetE (mulg1, rcosetM). Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)