∀ {C : Type u_2} [inst : CategoryTheory.Category.{u_1, u_2} C] [inst_1 : CategoryTheory.Preadditive C]
  [inst_2 : CategoryTheory.Limits.HasZeroObject C] [inst_3 : CategoryTheory.HasShift C ℤ]
  [inst_4 : ∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive] [inst_5 : CategoryTheory.Pretriangulated C]
  (t : CategoryTheory.Triangulated.TStructure C) (n : ℤ) {X_1 Y_1 Z : C} (f : X_1 ⟶ Y_1) (g : Y_1 ⟶ Z),
  CategoryTheory.Triangulated.TStructure.TruncAux.triangleMap✝ t n (CategoryTheory.CategoryStruct.comp f g) =
    CategoryTheory.CategoryStruct.comp (CategoryTheory.Triangulated.TStructure.TruncAux.triangleMap✝ t n f)
      (CategoryTheory.Triangulated.TStructure.TruncAux.triangleMap✝ t n g)