proposition: Lemma conjUg A B x : (A :|: B) :^ x = A :^ x :|: B :^ x.
proof: Proof. by rewrite !conjg_preim preimsetU. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)