Lemma istriangle_Rabs : ∏ x y : Reals, (Rabs (x + y)%R <= Rabs x + Rabs y)%NR. Proof. exact istriangle_hr_abs. Qed.
Require Import UniMath.Foundations.Preamble. Require Import UniMath.MoreFoundations.Orders. Require Import UniMath.MoreFoundations.Tactics. Require Import UniMath.OrderTheory.Lattice.Lattice. Require Import UniMath.RealNumbers.Prelim. Require Import UniMath.RealNumbers.Sets. Require Import UniMath.RealNumbers.NonnegativeRationals.