Module: Mathlib.CategoryTheory.Triangulated.TStructure.ETrunc

Goal state before:
pp: C : Type u_1
inst✝⁵ : Category.{v_1, u_1} C
inst✝⁴ : Preadditive C
inst✝³ : HasZeroObject C
inst✝² : HasShift C ℤ
inst✝¹ : ∀ (n : ℤ), (shiftFunctor C n).Additive
inst✝ : Pretriangulated C
t : TStructure C
x y z : EInt
f : x ⟶ y
g : y ⟶ z
⊢ WithBotTop.rec (motive := fun {x} ↦
      (x ⟶ z) → (WithBotTop.rec 0 t.truncLT (𝟭 C) x ⟶ WithBotTop.rec 0 t.truncLT (𝟭 C) z))
      (fun f ↦
        WithBotTop.rec (motive := fun {y} ↦
          (⊥ ⟶ y) → (WithBotTop.rec 0 t.truncLT (𝟭 C) ⊥ ⟶ WithBotTop.rec 0 t.truncLT (𝟭 C) y))
          (fun f ↦ 𝟙 (WithBotTop.rec 0 t.truncLT (𝟭 C) ⊥)) (fun b f ↦ 0) (fun f ↦ 0) z f)
      (fun a f ↦
        WithBotTop.rec (motive := fun {y} ↦
          (WithBotTop.coe a ⟶ y) →
            (WithBotTop.rec 0 t.truncLT (𝟭 C) (WithBotTop.coe a) ⟶ WithBotTop.rec 0 t.truncLT (𝟭 C) y))
          (fun f ↦ 0) (fun b f ↦ t.natTransTruncLTOfLE a b ⋯) (fun f ↦ t.truncLTι a) z f)
      (fun f ↦
        WithBotTop.rec (motive := fun {y} ↦
          (⊤ ⟶ y) → (WithBotTop.rec 0 t.truncLT (𝟭 C) ⊤ ⟶ WithBotTop.rec 0 t.truncLT (𝟭 C) y)) (fun f ↦ 0) (fun b f ↦ 0)
          (fun f ↦ 𝟙 (WithBotTop.rec 0 t.truncLT (𝟭 C) ⊤)) z f)
      x (f ≫ g) =
    WithBotTop.rec (motive := fun {x} ↦
        (x ⟶ y) → (WithBotTop.rec 0 t.truncLT (𝟭 C) x ⟶ WithBotTop.rec 0 t.truncLT (𝟭 C) y))
        (fun f ↦
          WithBotTop.rec (motive := fun {y} ↦
            (⊥ ⟶ y) → (WithBotTop.rec 0 t.truncLT (𝟭 C) ⊥ ⟶ WithBotTop.rec 0 t.truncLT (𝟭 C) y))
            (fun f ↦ 𝟙 (WithBotTop.rec 0 t.truncLT (𝟭 C) ⊥)) (fun b f ↦ 0) (fun f ↦ 0) y f)
        (fun a f ↦
          WithBotTop.rec (motive := fun {y} ↦
            (WithBotTop.coe a ⟶ y) →
              (WithBotTop.rec 0 t.truncLT (𝟭 C) (WithBotTop.coe a) ⟶ WithBotTop.rec 0 t.truncLT (𝟭 C) y))
            (fun f ↦ 0) (fun b f ↦ t.natTransTruncLTOfLE a b ⋯) (fun f ↦ t.truncLTι a) y f)
        (fun f ↦
          WithBotTop.rec (motive := fun {y} ↦
            (⊤ ⟶ y) → (WithBotTop.rec 0 t.truncLT (𝟭 C) ⊤ ⟶ WithBotTop.rec 0 t.truncLT (𝟭 C) y)) (fun f ↦ 0)
            (fun b f ↦ 0) (fun f ↦ 𝟙 (WithBotTop.rec 0 t.truncLT (𝟭 C) ⊤)) y f)
        x f ≫
      WithBotTop.rec (motive := fun {x} ↦
        (x ⟶ z) → (WithBotTop.rec 0 t.truncLT (𝟭 C) x ⟶ WithBotTop.rec 0 t.truncLT (𝟭 C) z))
        (fun f ↦
          WithBotTop.rec (motive := fun {y} ↦
            (⊥ ⟶ y) → (WithBotTop.rec 0 t.truncLT (𝟭 C) ⊥ ⟶ WithBotTop.rec 0 t.truncLT (𝟭 C) y))
            (fun f ↦ 𝟙 (WithBotTop.rec 0 t.truncLT (𝟭 C) ⊥)) (fun b f ↦ 0) (fun f ↦ 0) z f)
        (fun a f ↦
          WithBotTop.rec (motive := fun {y} ↦
            (WithBotTop.coe a ⟶ y) →
              (WithBotTop.rec 0 t.truncLT (𝟭 C) (WithBotTop.coe a) ⟶ WithBotTop.rec 0 t.truncLT (𝟭 C) y))
            (fun f ↦ 0) (fun b f ↦ t.natTransTruncLTOfLE a b ⋯) (fun f ↦ t.truncLTι a) z f)
        (fun f ↦
          WithBotTop.rec (motive := fun {y} ↦
            (⊤ ⟶ y) → (WithBotTop.rec 0 t.truncLT (𝟭 C) ⊤ ⟶ WithBotTop.rec 0 t.truncLT (𝟭 C) y)) (fun f ↦ 0)
            (fun b f ↦ 0) (fun f ↦ 𝟙 (WithBotTop.rec 0 t.truncLT (𝟭 C) ⊤)) z f)
        y g

Tactic:
by
    have f' := leOfHom f
    have g' := leOfHom g
    induction x using WithBotTop.rec <;> induction y using WithBotTop.rec <;>
      induction z using WithBotTop.rec <;> cat_disch

Goal state after: