proposition: Lemma opp_respects : forall q1 q2, equiv q1 q2 -> equiv (opp q1) (opp q2).
proof: Proof. unfold equiv;simpl. intros q1 q2 E. rewrite !(plus_comm (neg _)). symmetry. apply E. Qed.
imports: HoTT.HIT.quotient HoTT.TruncType HoTT.Basics.Trunc HoTT.Classes.implementations.peano_naturals HoTT.Classes.interfaces.abstract_algebra HoTT.Classes.interfaces.orders HoTT.Classes.interfaces.integers HoTT.Classes.theory.rings HoTT.Classes.theory.groups HoTT.Classes.theory.apartness HoTT.Classes.orders.sum HoTT.Classes.orders.rings HoTT.Classes.tactics.ring_tac HoTT.Classes.theory.naturals