C : Type u_2
inst✝¹ : Category C
inst✝ : Preadditive C
⊢ (∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasEqualizer (𝟙 X) p) ↔ ∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasKernel p
C : Type u_2
inst✝¹ : Category C
inst✝ : Preadditive C
⊢ IsIdempotentComplete C ↔ ∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasKernel p
rw [isIdempotentComplete_iff_hasEqualizer_of_id_and_idempotent]
case mp
C : Type u_2
inst✝¹ : Category C
inst✝ : Preadditive C
⊢ (∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasEqualizer (𝟙 X) p) → ∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasKernel p

case mpr
C : Type u_2
inst✝¹ : Category C
inst✝ : Preadditive C
⊢ (∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasKernel p) → ∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasEqualizer (𝟙 X) p
C : Type u_2
inst✝¹ : Category C
inst✝ : Preadditive C
⊢ (∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasEqualizer (𝟙 X) p) ↔ ∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasKernel p
constructor
case mp
C : Type u_2
inst✝¹ : Category C
inst✝ : Preadditive C
h : ∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasEqualizer (𝟙 X) p
X : C
p : X ⟶ X
hp : p ≫ p = p
⊢ HasKernel p
case mp
C : Type u_2
inst✝¹ : Category C
inst✝ : Preadditive C
⊢ (∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasEqualizer (𝟙 X) p) → ∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasKernel p
intro h X p hp
case mp
C : Type u_2
inst✝¹ : Category C
inst✝ : Preadditive C
h : ∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasEqualizer (𝟙 X) p
X : C
p : X ⟶ X
hp : p ≫ p = p
this : HasEqualizer (𝟙 X) (𝟙 X - p)
⊢ HasKernel p
case mp
C : Type u_2
inst✝¹ : Category C
inst✝ : Preadditive C
h : ∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasEqualizer (𝟙 X) p
X : C
p : X ⟶ X
hp : p ≫ p = p
⊢ HasKernel p
haveI : HasEqualizer (𝟙 X) (𝟙 X - p) := h X (𝟙 _ - p) (idem_of_id_sub_idem p hp)
case h.e'_6
C : Type u_2
inst✝¹ : Category C
inst✝ : Preadditive C
h : ∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasEqualizer (𝟙 X) p
X : C
p : X ⟶ X
hp : p ≫ p = p
this : HasEqualizer (𝟙 X) (𝟙 X - p)
⊢ p = 𝟙 X - (𝟙 X - p)
case mp
C : Type u_2
inst✝¹ : Category C
inst✝ : Preadditive C
h : ∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasEqualizer (𝟙 X) p
X : C
p : X ⟶ X
hp : p ≫ p = p
this : HasEqualizer (𝟙 X) (𝟙 X - p)
⊢ HasKernel p
convert hasKernel_of_hasEqualizer (𝟙 X) (𝟙 X - p)
no goals
case h.e'_6
C : Type u_2
inst✝¹ : Category C
inst✝ : Preadditive C
h : ∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasEqualizer (𝟙 X) p
X : C
p : X ⟶ X
hp : p ≫ p = p
this : HasEqualizer (𝟙 X) (𝟙 X - p)
⊢ p = 𝟙 X - (𝟙 X - p)
rw [sub_sub_cancel]
case mpr
C : Type u_2
inst✝¹ : Category C
inst✝ : Preadditive C
h : ∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasKernel p
X : C
p : X ⟶ X
hp : p ≫ p = p
⊢ HasEqualizer (𝟙 X) p
case mpr
C : Type u_2
inst✝¹ : Category C
inst✝ : Preadditive C
⊢ (∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasKernel p) → ∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasEqualizer (𝟙 X) p
intro h X p hp
case mpr
C : Type u_2
inst✝¹ : Category C
inst✝ : Preadditive C
h : ∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasKernel p
X : C
p : X ⟶ X
hp : p ≫ p = p
this : HasKernel (𝟙 X - p)
⊢ HasEqualizer (𝟙 X) p
case mpr
C : Type u_2
inst✝¹ : Category C
inst✝ : Preadditive C
h : ∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasKernel p
X : C
p : X ⟶ X
hp : p ≫ p = p
⊢ HasEqualizer (𝟙 X) p
haveI : HasKernel (𝟙 _ - p) := h X (𝟙 _ - p) (idem_of_id_sub_idem p hp)
no goals
case mpr
C : Type u_2
inst✝¹ : Category C
inst✝ : Preadditive C
h : ∀ (X : C) (p : X ⟶ X), p ≫ p = p → HasKernel p
X : C
p : X ⟶ X
hp : p ≫ p = p
this : HasKernel (𝟙 X - p)
⊢ HasEqualizer (𝟙 X) p
apply Preadditive.hasEqualizer_of_hasKernel