proposition: Lemma pl_0_r@{} x : equiv (x + 0) x.
proof: Proof. red;simpl. rewrite 2!mult_1_r, mult_0_l, plus_0_r. reflexivity. Qed.
imports: HoTT.HIT.quotient HoTT.Basics.Trunc HoTT.Classes.interfaces.abstract_algebra HoTT.Classes.theory.dec_fields