proposition: Lemma pgroupJ pi G x : pi.-group (G :^ x) = pi.-group G.
proof: Proof. by rewrite /pgroup cardJg. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(fintype bigop finset prime fingroup morphism) mathcomp(gfunctor automorphism quotient action gproduct) mathcomp(cyclic)