proposition: Lemma isassoc_CCDRplus : ∏ x y z : X, x + y + z = x + (y + z).
proof: Proof. now apply rigassoc1. Qed.
imports: UniMath.Algebra.DivisionRig UniMath.Algebra.Domains_and_Fields UniMath.Algebra.Apartness UniMath.MoreFoundations.Tactics