∀ {R : Type u_1} {C : Type u_2} [inst : Semiring R] [inst_1 : CategoryTheory.Category.{v_1, u_2} C]
  [inst_2 : CategoryTheory.Preadditive C] [inst_3 : CategoryTheory.Linear R C] {S₁ S₂ : CategoryTheory.ShortComplex C}
  {φ₁ φ₂ : S₁ ⟶ S₂} (h : CategoryTheory.ShortComplex.Homotopy φ₁ φ₂) (a : R), (h.smul a).h₂ = a • h.h₂