-- Mathlib/CategoryTheory/Triangulated/Opposite/Basic.lean
lemma shiftFunctorAdd'_op_hom_app (X : Cᵒᵖ) (a₁ a₂ a₃ : ℤ) (h : a₁ + a₂ = a₃)
    (b₁ b₂ b₃ : ℤ) (h₁ : a₁ + b₁ = 0) (h₂ : a₂ + b₂ = 0) (h₃ : a₃ + b₃ = 0) :
    (shiftFunctorAdd' Cᵒᵖ a₁ a₂ a₃ h).hom.app X =
      (shiftFunctorOpIso C _ _ h₃).hom.app X ≫
        ((shiftFunctorAdd' C b₁ b₂ b₃ (by omega)).inv.app X.unop).op ≫
        (shiftFunctorOpIso C _ _ h₂).inv.app _ ≫
        (shiftFunctor Cᵒᵖ a₂).map ((shiftFunctorOpIso C _ _ h₁).inv.app X)

Proof state:
C : Type u_1
inst✝¹ : Category.{u_2, u_1} C
inst✝ : HasShift C ℤ
X : Cᵒᵖ
a₁ a₂ a₃ : ℤ
h : a₁ + a₂ = a₃
b₁ b₂ b₃ : ℤ
h₁ : a₁ + b₁ = 0
h₂ : a₂ + b₂ = 0
h₃ : a₃ + b₃ = 0
⊢ (pullbackShiftIso (OppositeShift C ℤ)
              (AddMonoidHom.mk' (fun n => -n) CategoryTheory.Pretriangulated.Opposite.OppositeShiftAux.proof_1) a₃ b₃
              ⋯).hom.app
        X ≫
      ((shiftFunctorAdd' C b₁ b₂ b₃ ⋯).inv.app (Opposite.unop X)).op ≫
        (pullbackShiftIso (OppositeShift C ℤ)
                  (AddMonoidHom.mk' (fun n => -n) CategoryTheory.Pretriangulated.Opposite.OppositeShiftAux.proof_1) a₂
                  b₂ ⋯).inv.app
            ((shiftFunctor (OppositeShift C ℤ) b₁).obj X) ≫
          (shiftFunctor
                (PullbackShift (OppositeShift C ℤ)
                  (AddMonoidHom.mk' (fun n => -n) CategoryTheory.Pretriangulated.Opposite.OppositeShiftAux.proof_1))
                a₂).map
            ((pullbackShiftIso (OppositeShift C ℤ)
                    (AddMonoidHom.mk' (fun n => -n) CategoryTheory.Pretriangulated.Opposite.OppositeShiftAux.proof_1) a₁
                    b₁ ⋯).inv.app
              X) =
    (shiftFunctorOpIso C a₃ b₃ h₃).hom.app X ≫
      ((shiftFunctorAdd' C b₁ b₂ b₃ ⋯).inv.app (Opposite.unop X)).op ≫
        (shiftFunctorOpIso C a₂ b₂ h₂).inv.app (Opposite.op ((shiftFunctor C b₁).toPrefunctor.1 (Opposite.unop X))) ≫
          (shiftFunctor Cᵒᵖ a₂).map ((shiftFunctorOpIso C a₁ b₁ h₁).inv.app X)

Tactic:
rfl

Result:
no goals

Proof state:
C : Type u_1
inst✝¹ : Category.{u_2, u_1} C
inst✝ : HasShift C ℤ
X : Cᵒᵖ
a₁ a₂ a₃ : ℤ
h : a₁ + a₂ = a₃
b₁ b₂ b₃ : ℤ
h₁ : a₁ + b₁ = 0
h₂ : a₂ + b₂ = 0
h₃ : a₃ + b₃ = 0
⊢ b₁ = (AddMonoidHom.mk' (fun n => -n) CategoryTheory.Pretriangulated.Opposite.OppositeShiftAux.proof_1) a₁

Tactic:
dsimp

Result:
C : Type u_1
inst✝¹ : Category.{u_2, u_1} C
inst✝ : HasShift C ℤ
X : Cᵒᵖ
a₁ a₂ a₃ : ℤ
h : a₁ + a₂ = a₃
b₁ b₂ b₃ : ℤ
h₁ : a₁ + b₁ = 0
h₂ : a₂ + b₂ = 0
h₃ : a₃ + b₃ = 0
⊢ b₁ = -a₁

Proof state:
C : Type u_1
inst✝¹ : Category.{u_2, u_1} C
inst✝ : HasShift C ℤ
X : Cᵒᵖ
a₁ a₂ a₃ : ℤ
h : a₁ + a₂ = a₃
b₁ b₂ b₃ : ℤ
h₁ : a₁ + b₁ = 0
h₂ : a₂ + b₂ = 0
h₃ : a₃ + b₃ = 0
⊢ b₃ = (AddMonoidHom.mk' (fun n => -n) CategoryTheory.Pretriangulated.Opposite.OppositeShiftAux.proof_1) a₃

Tactic:
dsimp

Result:
C : Type u_1
inst✝¹ : Category.{u_2, u_1} C
inst✝ : HasShift C ℤ
X : Cᵒᵖ
a₁ a₂ a₃ : ℤ
h : a₁ + a₂ = a₃
b₁ b₂ b₃ : ℤ
h₁ : a₁ + b₁ = 0
h₂ : a₂ + b₂ = 0
h₃ : a₃ + b₃ = 0
⊢ b₃ = -a₃

Proof state:
C : Type u_1
inst✝¹ : Category.{u_2, u_1} C
inst✝ : HasShift C ℤ
X : Cᵒᵖ
a₁ a₂ a₃ : ℤ
h : a₁ + a₂ = a₃
b₁ b₂ b₃ : ℤ
h₁ : a₁ + b₁ = 0
h₂ : a₂ + b₂ = 0
h₃ : a₃ + b₃ = 0
⊢ b₁ = -a₁

Tactic:
omega

Result:
no goals