proposition: Lemma zero_sum : forall (x y : N), x + y = 0 -> x = 0 /\ y = 0.
proof: Proof. refine (from_nat_stmt nat (fun s => forall x y : s, x + y = 0 -> x = 0 /\ y = 0) _). simpl. apply plus_eq_zero. Qed.
imports: HoTT.Basics.Decidable HoTT.Classes.interfaces.orders HoTT.Classes.implementations.peano_naturals HoTT.Classes.theory.rings HoTT.Classes.isomorphisms.rings HoTT.Classes.interfaces.naturals