(I : Ideal R) : I + I ↔ I. Proof. apply ideal_subset_antisymm. 1: by rapply ideal_sum_smallest. rapply ideal_sum_subset_l. Defined.
Require Import Basics Types. Require Import Spaces.Finite.Fin. Require Import Classes.interfaces.canonical_names. Require Import Algebra.Rings.Ring. Require Import Algebra.Groups.Subgroup. Require Import Algebra.AbGroups. Require Import WildCat.Core. Module Import Notation.