Module: Mathlib.Algebra.Homology.HomotopyCategory.MappingCone

Goal state before:
pp: case left
C : Type u_1
D : Type u_2
inst✝⁶ : Category.{v, u_1} C
inst✝⁵ : Category.{v', u_2} D
inst✝⁴ : Preadditive C
inst✝³ : Preadditive D
F G : CochainComplex C ℤ
φ : F ⟶ G
inst✝² : HasHomotopyCofiber φ
H : C ⥤ D
inst✝¹ : H.Additive
inst✝ : HasHomotopyCofiber ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ)
n : ℤ
⊢ (H.map ((↑(fst φ)).v n (n + 1) ⋯) ≫ (inl ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ)).v (n + 1) n ⋯ +
        H.map ((snd φ).v n n ⋯) ≫ (inr ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ)).f n) ≫
      (-(↑(fst ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ))).v n (n + 1) ⋯ ≫
          ((H.mapHomologicalComplex (ComplexShape.up ℤ)).obj F).d (n + 1) (n + 2)) =
    ((H.mapHomologicalComplex (ComplexShape.up ℤ)).obj (mappingCone φ)).d n (n + 1) ≫
      (H.map ((↑(fst φ)).v (n + 1) (n + 2) ⋯) ≫
            (inl ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ)).v (n + 2) (n + 1) ⋯ +
          H.map ((snd φ).v (n + 1) (n + 1) ⋯) ≫ (inr ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ)).f (n + 1)) ≫
        (↑(fst ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ))).v (n + 1) (n + 2)
          (CochainComplex.mappingCone.mapHomologicalComplexIso._proof_1 n)

pp: case right
C : Type u_1
D : Type u_2
inst✝⁶ : Category.{v, u_1} C
inst✝⁵ : Category.{v', u_2} D
inst✝⁴ : Preadditive C
inst✝³ : Preadditive D
F G : CochainComplex C ℤ
φ : F ⟶ G
inst✝² : HasHomotopyCofiber φ
H : C ⥤ D
inst✝¹ : H.Additive
inst✝ : HasHomotopyCofiber ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ)
n : ℤ
⊢ (H.map ((↑(fst φ)).v n (n + 1) ⋯) ≫ (inl ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ)).v (n + 1) n ⋯ +
        H.map ((snd φ).v n n ⋯) ≫ (inr ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ)).f n) ≫
      ((↑(fst ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ))).v n (n + 1) ⋯ ≫
          ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ).f (n + 1) +
        (snd ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ)).v n n ⋯ ≫
          ((H.mapHomologicalComplex (ComplexShape.up ℤ)).obj G).d n (n + 1)) =
    ((H.mapHomologicalComplex (ComplexShape.up ℤ)).obj (mappingCone φ)).d n (n + 1) ≫
      (H.map ((↑(fst φ)).v (n + 1) (n + 2) ⋯) ≫
            (inl ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ)).v (n + 2) (n + 1) ⋯ +
          H.map ((snd φ).v (n + 1) (n + 1) ⋯) ≫ (inr ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ)).f (n + 1)) ≫
        (snd ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ)).v (n + 1) (n + 1) ⋯

Tactic:
· dsimp
      simp only [Functor.mapHomologicalComplex_obj_X, comp_neg, add_comp, assoc, inl_v_fst_v_assoc,
        inr_f_fst_v_assoc, zero_comp, comp_zero, add_zero, inl_v_fst_v, comp_id, inr_f_fst_v,
        ← H.map_comp, d_fst_v φ n (n + 1) (n + 2) rfl (by lia), Functor.map_neg]

Goal state after:
case right
C : Type u_1
D : Type u_2
inst✝⁶ : Category.{v, u_1} C
inst✝⁵ : Category.{v', u_2} D
inst✝⁴ : Preadditive C
inst✝³ : Preadditive D
F G : CochainComplex C ℤ
φ : F ⟶ G
inst✝² : HasHomotopyCofiber φ
H : C ⥤ D
inst✝¹ : H.Additive
inst✝ : HasHomotopyCofiber ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ)
n : ℤ
⊢ (H.map ((↑(fst φ)).v n (n + 1) ⋯) ≫ (inl ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ)).v (n + 1) n ⋯ +
        H.map ((snd φ).v n n ⋯) ≫ (inr ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ)).f n) ≫
      ((↑(fst ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ))).v n (n + 1) ⋯ ≫
          ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ).f (n + 1) +
        (snd ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ)).v n n ⋯ ≫
          ((H.mapHomologicalComplex (ComplexShape.up ℤ)).obj G).d n (n + 1)) =
    ((H.mapHomologicalComplex (ComplexShape.up ℤ)).obj (mappingCone φ)).d n (n + 1) ≫
      (H.map ((↑(fst φ)).v (n + 1) (n + 2) ⋯) ≫
            (inl ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ)).v (n + 2) (n + 1) ⋯ +
          H.map ((snd φ).v (n + 1) (n + 1) ⋯) ≫ (inr ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ)).f (n + 1)) ≫
        (snd ((H.mapHomologicalComplex (ComplexShape.up ℤ)).map φ)).v (n + 1) (n + 1) ⋯