(F F' : Functor C D) (T : NaturalTransformation F F') : T o 1 = T. Proof. path_natural_transformation; auto with morphism. Qed.
Require Import Category.Core Functor.Core Functor.Identity Functor.Composition.Core NaturalTransformation.Core NaturalTransformation.Identity NaturalTransformation.Composition.Core NaturalTransformation.Paths.