proposition: Lemma ideal_sum_zero_l I : ideal_zero R + I ↔ I.
proof: Proof. apply ideal_subset_antisymm. 1: apply ideal_sum_smallest. 1: apply ideal_zero_subset. 1: reflexivity. apply ideal_sum_subset_r. Defined.
imports: Basics Types Spaces.Finite.Fin Classes.interfaces.abstract_algebra Algebra.Rings.CRing Algebra.AbGroups