∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] [inst_1 : CategoryTheory.HasShift C ℤ]
  {T₁ T₂ : CategoryTheory.Pretriangulated.Triangle C} [inst_2 : CategoryTheory.Preadditive C]
  [inst_3 : ∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive] (f g : T₁ ⟶ T₂), (f - g).hom₂ = f.hom₂ - g.hom₂