proposition: Lemma pl_0_l@{} x : equiv (0 + x) x.
proof: Proof. red;simpl. rewrite mult_1_r, mult_0_l, mult_1_l, plus_0_l. reflexivity. Qed.
imports: HoTT.HIT.quotient HoTT.Basics.Trunc HoTT.Classes.interfaces.abstract_algebra HoTT.Classes.theory.dec_fields