-- Mathlib/CategoryTheory/Preadditive/OfBiproducts.lean
theorem isUnital_leftAdd : EckmannHilton.IsUnital (· +ₗ ·) 0

Proof state:
case h₀
C : Type u
inst✝² : Category.{v, u} C
inst✝¹ : HasZeroMorphisms C
inst✝ : HasBinaryBiproducts C
X Y : C
f : X ⟶ Y
⊢ biprod.lift 0 f ≫ biprod.fst = (f ≫ biprod.inr) ≫ biprod.fst

Tactic:
simp

Result:
no goals

Proof state:
C : Type u
inst✝² : Category.{v, u} C
inst✝¹ : HasZeroMorphisms C
inst✝ : HasBinaryBiproducts C
X Y : C
f : X ⟶ Y
⊢ biprod.lift 0 f = f ≫ biprod.inr

Tactic:
ext

Result:
case h₀
C : Type u
inst✝² : Category.{v, u} C
inst✝¹ : HasZeroMorphisms C
inst✝ : HasBinaryBiproducts C
X Y : C
f : X ⟶ Y
⊢ biprod.lift 0 f ≫ biprod.fst = (f ≫ biprod.inr) ≫ biprod.fst

case h₁
C : Type u
inst✝² : Category.{v, u} C
inst✝¹ : HasZeroMorphisms C
inst✝ : HasBinaryBiproducts C
X Y : C
f : X ⟶ Y
⊢ biprod.lift 0 f ≫ biprod.snd = (f ≫ biprod.inr) ≫ biprod.snd

Proof state:
C : Type u
inst✝² : Category.{v, u} C
inst✝¹ : HasZeroMorphisms C
inst✝ : HasBinaryBiproducts C
X Y : C
hr : ∀ (f : X ⟶ Y), biprod.lift 0 f = f ≫ biprod.inr
hl : ∀ (f : X ⟶ Y), biprod.lift f 0 = f ≫ biprod.inl
⊢ EckmannHilton.IsUnital (fun x1 x2 => leftAdd X Y x1 x2) 0

Tactic:
exact {
  left_id := fun f => by simp [hr f, leftAdd, Category.assoc, Category.comp_id, biprod.inr_desc],
  right_id := fun f => by simp [hl f, leftAdd, Category.assoc, Category.comp_id, biprod.inl_desc]
}

Result:
no goals

Proof state:
case h₁
C : Type u
inst✝² : Category.{v, u} C
inst✝¹ : HasZeroMorphisms C
inst✝ : HasBinaryBiproducts C
X Y : C
hr : ∀ (f : X ⟶ Y), biprod.lift 0 f = f ≫ biprod.inr
f : X ⟶ Y
⊢ biprod.lift f 0 ≫ biprod.snd = (f ≫ biprod.inl) ≫ biprod.snd

Tactic:
simp [biprod.lift_snd, Category.assoc, biprod.inl_snd, comp_zero]

Result:
no goals

Proof state:
case h₀
C : Type u
inst✝² : Category.{v, u} C
inst✝¹ : HasZeroMorphisms C
inst✝ : HasBinaryBiproducts C
X Y : C
hr : ∀ (f : X ⟶ Y), biprod.lift 0 f = f ≫ biprod.inr
f : X ⟶ Y
⊢ biprod.lift f 0 ≫ biprod.fst = (f ≫ biprod.inl) ≫ biprod.fst

Tactic:
simp

Result:
no goals

Proof state:
C : Type u
inst✝² : Category.{v, u} C
inst✝¹ : HasZeroMorphisms C
inst✝ : HasBinaryBiproducts C
X Y : C
hr : ∀ (f : X ⟶ Y), biprod.lift 0 f = f ≫ biprod.inr
hl : ∀ (f : X ⟶ Y), biprod.lift f 0 = f ≫ biprod.inl
f : X ⟶ Y
⊢ leftAdd X Y 0 f = f

Tactic:
simp [hr f, leftAdd, Category.assoc, Category.comp_id, biprod.inr_desc]

Result:
no goals

Proof state:
C : Type u
inst✝² : Category.{v, u} C
inst✝¹ : HasZeroMorphisms C
inst✝ : HasBinaryBiproducts C
X Y : C
hr : ∀ (f : X ⟶ Y), biprod.lift 0 f = f ≫ biprod.inr
⊢ ∀ (f : X ⟶ Y), biprod.lift f 0 = f ≫ biprod.inl

Tactic:
intro f

Result:
C : Type u
inst✝² : Category.{v, u} C
inst✝¹ : HasZeroMorphisms C
inst✝ : HasBinaryBiproducts C
X Y : C
hr : ∀ (f : X ⟶ Y), biprod.lift 0 f = f ≫ biprod.inr
f : X ⟶ Y
⊢ biprod.lift f 0 = f ≫ biprod.inl

Proof state:
case h₁
C : Type u
inst✝² : Category.{v, u} C
inst✝¹ : HasZeroMorphisms C
inst✝ : HasBinaryBiproducts C
X Y : C
f : X ⟶ Y
⊢ biprod.lift 0 f ≫ biprod.snd = (f ≫ biprod.inr) ≫ biprod.snd

Tactic:
simp [biprod.lift_fst, Category.assoc, biprod.inr_fst, comp_zero]

Result:
no goals

Proof state:
C : Type u
inst✝² : Category.{v, u} C
inst✝¹ : HasZeroMorphisms C
inst✝ : HasBinaryBiproducts C
X Y : C
⊢ ∀ (f : X ⟶ Y), biprod.lift 0 f = f ≫ biprod.inr

Tactic:
intro f

Result:
C : Type u
inst✝² : Category.{v, u} C
inst✝¹ : HasZeroMorphisms C
inst✝ : HasBinaryBiproducts C
X Y : C
f : X ⟶ Y
⊢ biprod.lift 0 f = f ≫ biprod.inr

Proof state:
C : Type u
inst✝² : Category.{v, u} C
inst✝¹ : HasZeroMorphisms C
inst✝ : HasBinaryBiproducts C
X Y : C
hr : ∀ (f : X ⟶ Y), biprod.lift 0 f = f ≫ biprod.inr
f : X ⟶ Y
⊢ biprod.lift f 0 = f ≫ biprod.inl

Tactic:
ext

Result:
case h₀
C : Type u
inst✝² : Category.{v, u} C
inst✝¹ : HasZeroMorphisms C
inst✝ : HasBinaryBiproducts C
X Y : C
hr : ∀ (f : X ⟶ Y), biprod.lift 0 f = f ≫ biprod.inr
f : X ⟶ Y
⊢ biprod.lift f 0 ≫ biprod.fst = (f ≫ biprod.inl) ≫ biprod.fst

case h₁
C : Type u
inst✝² : Category.{v, u} C
inst✝¹ : HasZeroMorphisms C
inst✝ : HasBinaryBiproducts C
X Y : C
hr : ∀ (f : X ⟶ Y), biprod.lift 0 f = f ≫ biprod.inr
f : X ⟶ Y
⊢ biprod.lift f 0 ≫ biprod.snd = (f ≫ biprod.inl) ≫ biprod.snd

Proof state:
C : Type u
inst✝² : Category.{v, u} C
inst✝¹ : HasZeroMorphisms C
inst✝ : HasBinaryBiproducts C
X Y : C
hr : ∀ (f : X ⟶ Y), biprod.lift 0 f = f ≫ biprod.inr
hl : ∀ (f : X ⟶ Y), biprod.lift f 0 = f ≫ biprod.inl
f : X ⟶ Y
⊢ leftAdd X Y f 0 = f

Tactic:
simp [hl f, leftAdd, Category.assoc, Category.comp_id, biprod.inl_desc]

Result:
no goals