proposition: Lemma pHallJ2 pi G H x : pi.-Hall(G :^ x) (H :^ x) = pi.-Hall(G) H.
proof: Proof. by rewrite !pHallE conjSg !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)