proposition: Theorem Comma_Product {C : Category} {D : Category} (F : C ⟶ 1) (G : D ⟶ 1) : (F ↓ G) ≅[Cat] C ∏ D.
proof: Proof. simpl_cat. Qed.
imports: Category.Lib Category.Theory.Category Category.Theory.Isomorphism Category.Theory.Functor Category.Theory.Natural.Transformation Category.Construction.Comma Category.Construction.Product Category.Instance.Cat Category.Instance.One