proposition: Lemma Rmult_gt_0_lt_compat : forall r1 r2 r3 r4, r3 > 0 -> r2 > 0 -> r1 < r2 -> r3 < r4 -> r1 * r3 < r2 * r4.
proof: Proof. now intros r1 r2 r3 r4 H1%Rgt_ge; apply Rmult_ge_0_gt_0_lt_compat. Qed.
imports: RelationClasses Raxioms Rpow_def ZArith ZArithRing RealField