English
Given η : f ⟶ f', θ : g ⟶ g', κ : h ⟶ h', the horizontal composition is associative up to HEq: HEq (hComp (hComp η θ) κ) (hComp η (hComp θ κ)).
Русский
При η : f ⟶ f', θ : g ⟶ g', κ : h ⟶ h' горизонтальная композиция ассоциируется в терминах HEq: HEq (hComp (hComp η θ) κ) (hComp η (hComp θ κ)).
LaTeX
$$$ HEq\\left( \\mathrm{hComp}(\\mathrm{hComp}(\\eta,\\theta), \\kappa) , \\mathrm{hComp}(\\eta, \\mathrm{hComp}(\\theta, \\kappa))\\right) $$$
Lean4
theorem hComp_id_heq {a b : CatEnriched C} {f f' : a ⟶ b} (η : f ⟶ f') : HEq (hComp η (𝟙 (𝟙 b))) η :=
by
rw [id_eq, ← Functor.map_id]
exact congr_arg_heq (·.map η) (e_comp_id (V := Cat) a b)