Module: Mathlib.Algebra.Homology.HomotopyCategory.Triangulated

Goal state before:
pp: case refine_4
C : Type u_1
inst✝³ : Category.{v, u_1} C
inst✝² : Preadditive C
inst✝¹ : HasBinaryBiproducts C
X₁✝ X₂✝ X₃✝ : CochainComplex C ℤ
f : X₁✝ ⟶ X₂✝
g : X₂✝ ⟶ X₃✝
inst✝ : HasZeroObject C
X₁ X₂ X₃ : CochainComplex C ℤ
u₁₂ : X₁ ⟶ X₂
u₂₃ : X₂ ⟶ X₃
α : mappingCone.triangle u₁₂ ⟶ mappingCone.triangle (u₁₂ ≫ u₂₃) := mappingCone.triangleMap u₁₂ (u₁₂ ≫ u₂₃) (𝟙 X₁) u₂₃ ⋯
β : mappingCone.triangle (u₁₂ ≫ u₂₃) ⟶ mappingCone.triangle u₂₃ := mappingCone.triangleMap (u₁₂ ≫ u₂₃) u₂₃ u₁₂ (𝟙 X₃) ⋯
⊢ ((quotient C (ComplexShape.up ℤ)).map (mappingCone.triangle (u₁₂ ≫ u₂₃)).mor₃ ≫
        (Functor.commShiftIso (quotient C (ComplexShape.up ℤ)) 1).hom.app (mappingCone.triangle (u₁₂ ≫ u₂₃)).obj₁) ≫
      (CategoryTheory.shiftFunctor (HomotopyCategory C (ComplexShape.up ℤ)) 1).map
        ((quotient C (ComplexShape.up ℤ)).map (mappingCone.triangle u₁₂).mor₁) =
    (quotient C (ComplexShape.up ℤ)).map β.hom₃ ≫
      (quotient C (ComplexShape.up ℤ)).map (mappingCone.triangle u₂₃).mor₃ ≫
        (Functor.commShiftIso (quotient C (ComplexShape.up ℤ)) 1).hom.app (mappingCone.triangle u₂₃).obj₁

pp: case refine_5
C : Type u_1
inst✝³ : Category.{v, u_1} C
inst✝² : Preadditive C
inst✝¹ : HasBinaryBiproducts C
X₁✝ X₂✝ X₃✝ : CochainComplex C ℤ
f : X₁✝ ⟶ X₂✝
g : X₂✝ ⟶ X₃✝
inst✝ : HasZeroObject C
X₁ X₂ X₃ : CochainComplex C ℤ
u₁₂ : X₁ ⟶ X₂
u₂₃ : X₂ ⟶ X₃
α : mappingCone.triangle u₁₂ ⟶ mappingCone.triangle (u₁₂ ≫ u₂₃) := mappingCone.triangleMap u₁₂ (u₁₂ ≫ u₂₃) (𝟙 X₁) u₂₃ ⋯
β : mappingCone.triangle (u₁₂ ≫ u₂₃) ⟶ mappingCone.triangle u₂₃ := mappingCone.triangleMap (u₁₂ ≫ u₂₃) u₂₃ u₁₂ (𝟙 X₃) ⋯
⊢ Triangle.mk ((quotient C (ComplexShape.up ℤ)).map α.hom₃) ((quotient C (ComplexShape.up ℤ)).map β.hom₃)
      (((quotient C (ComplexShape.up ℤ)).map (mappingCone.triangle u₂₃).mor₃ ≫
          (Functor.commShiftIso (quotient C (ComplexShape.up ℤ)) 1).hom.app (mappingCone.triangle u₂₃).obj₁) ≫
        (CategoryTheory.shiftFunctor (HomotopyCategory C (ComplexShape.up ℤ)) 1).map
          ((quotient C (ComplexShape.up ℤ)).map (mappingCone.triangle u₁₂).mor₂)) ∈
    distinguishedTriangles

Tactic:
· exact ((quotient _ _).mapTriangle.map β).comm₃

Goal state after:
case refine_5
C : Type u_1
inst✝³ : Category.{v, u_1} C
inst✝² : Preadditive C
inst✝¹ : HasBinaryBiproducts C
X₁✝ X₂✝ X₃✝ : CochainComplex C ℤ
f : X₁✝ ⟶ X₂✝
g : X₂✝ ⟶ X₃✝
inst✝ : HasZeroObject C
X₁ X₂ X₃ : CochainComplex C ℤ
u₁₂ : X₁ ⟶ X₂
u₂₃ : X₂ ⟶ X₃
α : mappingCone.triangle u₁₂ ⟶ mappingCone.triangle (u₁₂ ≫ u₂₃) := mappingCone.triangleMap u₁₂ (u₁₂ ≫ u₂₃) (𝟙 X₁) u₂₃ ⋯
β : mappingCone.triangle (u₁₂ ≫ u₂₃) ⟶ mappingCone.triangle u₂₃ := mappingCone.triangleMap (u₁₂ ≫ u₂₃) u₂₃ u₁₂ (𝟙 X₃) ⋯
⊢ Triangle.mk ((quotient C (ComplexShape.up ℤ)).map α.hom₃) ((quotient C (ComplexShape.up ℤ)).map β.hom₃)
      (((quotient C (ComplexShape.up ℤ)).map (mappingCone.triangle u₂₃).mor₃ ≫
          (Functor.commShiftIso (quotient C (ComplexShape.up ℤ)) 1).hom.app (mappingCone.triangle u₂₃).obj₁) ≫
        (CategoryTheory.shiftFunctor (HomotopyCategory C (ComplexShape.up ℤ)) 1).map
          ((quotient C (ComplexShape.up ℤ)).map (mappingCone.triangle u₁₂).mor₂)) ∈
    distinguishedTriangles