- now intros w; rewrite Rmin_left;[ | apply Rge_le, Ropp_le_ge_contravar].
- now intros w; rewrite Rmin_right; [ | apply Rge_le, Ropp_le_ge_contravar].
Qed.

(* Specifications: *)
Lemma Ropp_Rmin : forall x y, - Rmin x y = Rmax (-x) (-y).
intros x y; apply Rmin_case_strong.