proposition: Corollary fork_comp {x y z w : C} (f : y ~> z) (h : y ~> w) (g : x ~> y) : (f ∘ g) △ (h ∘ g) ≈ f △ h ∘ g.
proof: Proof. intros. symmetry. apply ump_products; split; rewrite !comp_assoc; cat. Qed.
imports: Category.Lib Category.Theory.Category Category.Theory.Isomorphism Category.Structure.Terminal