proposition: Lemma BQopp_sign x: ratp x -> (BQsign (BQopp x)) = BZopp (BQsign x).
proof: Proof. by move/BQ_P => [_ xq _ _]; rewrite /BQopp /BQsign pr1_pair BZopp_sign //. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)