proposition: Lemma isinjnatcoface ( i x y : nat ) : natcoface i x = natcoface i y -> x = y.
proof: Proof. intros p. change x with ( idfun _ x). rewrite <- ( natcofaceretractisretract i ). change y with ( idfun _ y ). rewrite <- ( natcofaceretractisretract i ). simpl. rewrite p. apply idpath. Defined.
imports: UniMath.Tactics.EnsureStructuredProofs UniMath.Foundations.PartA UniMath.Foundations.Propositions UniMath.Foundations.NaturalNumbers UniMath.Algebra.RigsAndRings UniMath.Algebra.Domains_and_Fields UniMath.NumberSystems.Integers UniMath.Algebra.Monoids