proposition: Lemma neg_mult x y : x < 0 -> y < 0 -> 0 < x * y.
proof: Proof. intros. rewrite <-(mult_0_r x). apply flip_neg_mult_l;trivial. Qed.
imports: HoTT.Classes.theory.apartness HoTT.Classes.interfaces.abstract_algebra HoTT.Classes.interfaces.orders HoTT.Classes.theory.rings HoTT.Classes.orders.orders HoTT.Classes.orders.maps