Theorem: CategoryTheory.Pretriangulated.Triangle.isZero₂_iff
File: Mathlib/CategoryTheory/Triangulated/Pretriangulated.lean

tactic: constructor
state_before: C : Type u
inst✝⁴ : Category.{v, u} C
inst✝³ : HasZeroObject C
inst✝² : HasShift C ℤ
inst✝¹ : Preadditive C
inst✝ : ∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive
hC : Pretriangulated C
T : Triangle C
hT : T ∈ distinguishedTriangles
⊢ IsZero T.obj₂ ↔ T.mor₁ = 0 ∧ T.mor₂ = 0
state_after: case mp
C : Type u
inst✝⁴ : Category.{v, u} C
inst✝³ : HasZeroObject C
inst✝² : HasShift C ℤ
inst✝¹ : Preadditive C
inst✝ : ∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive
hC : Pretriangulated C
T : Triangle C
hT : T ∈ distinguishedTriangles
⊢ IsZero T.obj₂ → T.mor₁ = 0 ∧ T.mor₂ = 0

case mpr
C : Type u
inst✝⁴ : Category.{v, u} C
inst✝³ : HasZeroObject C
inst✝² : HasShift C ℤ
inst✝¹ : Preadditive C
inst✝ : ∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive
hC : Pretriangulated C
T : Triangle C
hT : T ∈ distinguishedTriangles
⊢ T.mor₁ = 0 ∧ T.mor₂ = 0 → IsZero T.obj₂

tactic: intro h
state_before: case mp
C : Type u
inst✝⁴ : Category.{v, u} C
inst✝³ : HasZeroObject C
inst✝² : HasShift C ℤ
inst✝¹ : Preadditive C
inst✝ : ∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive
hC : Pretriangulated C
T : Triangle C
hT : T ∈ distinguishedTriangles
⊢ IsZero T.obj₂ → T.mor₁ = 0 ∧ T.mor₂ = 0
state_after: case mp
C : Type u
inst✝⁴ : Category.{v, u} C
inst✝³ : HasZeroObject C
inst✝² : HasShift C ℤ
inst✝¹ : Preadditive C
inst✝ : ∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive
hC : Pretriangulated C
T : Triangle C
hT : T ∈ distinguishedTriangles
h : IsZero T.obj₂
⊢ T.mor₁ = 0 ∧ T.mor₂ = 0

tactic: exact ⟨h.eq_of_tgt _ _, h.eq_of_src _ _⟩
state_before: case mp
C : Type u
inst✝⁴ : Category.{v, u} C
inst✝³ : HasZeroObject C
inst✝² : HasShift C ℤ
inst✝¹ : Preadditive C
inst✝ : ∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive
hC : Pretriangulated C
T : Triangle C
hT : T ∈ distinguishedTriangles
h : IsZero T.obj₂
⊢ T.mor₁ = 0 ∧ T.mor₂ = 0
state_after: no goals

tactic: intro ⟨h₁, h₂⟩
state_before: case mpr
C : Type u
inst✝⁴ : Category.{v, u} C
inst✝³ : HasZeroObject C
inst✝² : HasShift C ℤ
inst✝¹ : Preadditive C
inst✝ : ∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive
hC : Pretriangulated C
T : Triangle C
hT : T ∈ distinguishedTriangles
⊢ T.mor₁ = 0 ∧ T.mor₂ = 0 → IsZero T.obj₂
state_after: case mpr
C : Type u
inst✝⁴ : Category.{v, u} C
inst✝³ : HasZeroObject C
inst✝² : HasShift C ℤ
inst✝¹ : Preadditive C
inst✝ : ∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive
hC : Pretriangulated C
T : Triangle C
hT : T ∈ distinguishedTriangles
h₁ : T.mor₁ = 0
h₂ : T.mor₂ = 0
⊢ IsZero T.obj₂

tactic: obtain ⟨f, hf⟩ := coyoneda_exact₂ T hT (𝟙 _) (by rw [h₂, comp_zero])
state_before: case mpr
C : Type u
inst✝⁴ : Category.{v, u} C
inst✝³ : HasZeroObject C
inst✝² : HasShift C ℤ
inst✝¹ : Preadditive C
inst✝ : ∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive
hC : Pretriangulated C
T : Triangle C
hT : T ∈ distinguishedTriangles
h₁ : T.mor₁ = 0
h₂ : T.mor₂ = 0
⊢ IsZero T.obj₂
state_after: case mpr.intro
C : Type u
inst✝⁴ : Category.{v, u} C
inst✝³ : HasZeroObject C
inst✝² : HasShift C ℤ
inst✝¹ : Preadditive C
inst✝ : ∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive
hC : Pretriangulated C
T : Triangle C
hT : T ∈ distinguishedTriangles
h₁ : T.mor₁ = 0
h₂ : T.mor₂ = 0
f : T.obj₂ ⟶ T.obj₁
hf : 𝟙 T.obj₂ = f ≫ T.mor₁
⊢ IsZero T.obj₂

tactic: rw [IsZero.iff_id_eq_zero, hf, h₁, comp_zero]
state_before: case mpr.intro
C : Type u
inst✝⁴ : Category.{v, u} C
inst✝³ : HasZeroObject C
inst✝² : HasShift C ℤ
inst✝¹ : Preadditive C
inst✝ : ∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive
hC : Pretriangulated C
T : Triangle C
hT : T ∈ distinguishedTriangles
h₁ : T.mor₁ = 0
h₂ : T.mor₂ = 0
f : T.obj₂ ⟶ T.obj₁
hf : 𝟙 T.obj₂ = f ≫ T.mor₁
⊢ IsZero T.obj₂
state_after: no goals

tactic: rw [h₂, comp_zero]
state_before: C : Type u
inst✝⁴ : Category.{v, u} C
inst✝³ : HasZeroObject C
inst✝² : HasShift C ℤ
inst✝¹ : Preadditive C
inst✝ : ∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive
hC : Pretriangulated C
T : Triangle C
hT : T ∈ distinguishedTriangles
h₁ : T.mor₁ = 0
h₂ : T.mor₂ = 0
⊢ 𝟙 T.obj₂ ≫ T.mor₂ = 0
state_after: no goals