proposition: Lemma pmule_rle0 x y : 0 < x -> (x * y <= 0) = (y <= 0).
proof: Proof. by move=> xgt0; rewrite -oppe_ge0 -muleN pmule_rge0 ?oppe_ge0. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap) mathcomp(mathcomp_extra) signed