∀ (C : Type u_2) [inst : CategoryTheory.Category.{u_1, u_2} C] [inst_1 : CategoryTheory.Preadditive C]
  [inst_2 : CategoryTheory.HasShift C ℤ] [∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive] (a b n : ℤ)
  (h : a + b = n) (T : CategoryTheory.Pretriangulated.Triangle C),
  CategoryTheory.CategoryStruct.comp ((CategoryTheory.Pretriangulated.Triangle.shiftFunctor C n).obj T).mor₃
      ((CategoryTheory.shiftFunctor C 1).map ((CategoryTheory.shiftFunctorAdd' C a b n h).app T.obj₁).hom) =
    CategoryTheory.CategoryStruct.comp ((CategoryTheory.shiftFunctorAdd' C a b n h).app T.obj₃).hom
      (((CategoryTheory.Pretriangulated.Triangle.shiftFunctor C a).comp
              (CategoryTheory.Pretriangulated.Triangle.shiftFunctor C b)).obj
          T).mor₃