l3lab/ntp-mathlib huggingface dataset:
@[simp]
theorem Biprod.ofComponents_comp {X₁ X₂ Y₁ Y₂ Z₁ Z₂ : C} (f₁₁ : X₁ ⟶ Y₁) (f₁₂ : X₁ ⟶ Y₂)
    (f₂₁ : X₂ ⟶ Y₁) (f₂₂ : X₂ ⟶ Y₂) (g₁₁ : Y₁ ⟶ Z₁) (g₁₂ : Y₁ ⟶ Z₂) (g₂₁ : Y₂ ⟶ Z₁)
    (g₂₂ : Y₂ ⟶ Z₂) :
    Biprod.ofComponents f₁₁ f₁₂ f₂₁ f₂₂ ≫ Biprod.ofComponents g₁₁ g₁₂ g₂₁ g₂₂ =
      Biprod.ofComponents (f₁₁ ≫ g₁₁ + f₁₂ ≫ g₂₁) (f₁₁ ≫ g₁₂ + f₁₂ ≫ g₂₂) (f₂₁ ≫ g₁₁ + f₂₂ ≫ g₂₁)
        (f₂₁ ≫ g₁₂ + f₂₂ ≫ g₂₂) := by
  dsimp [Biprod.ofComponents]
  ext <;>
    

Proof state:
case h₁.h₀
C : Type u
inst✝² : Category.{v, u} C
inst✝¹ : Preadditive C
inst✝ : HasBinaryBiproducts C
X₁✝ X₂✝ Y₁✝ Y₂✝ : C
f₁₁✝ : X₁✝ ⟶ Y₁✝
f₁₂✝ : X₁✝ ⟶ Y₂✝
f₂₁✝ : X₂✝ ⟶ Y₁✝
f₂₂✝ : X₂✝ ⟶ Y₂✝
X₁ X₂ Y₁ Y₂ Z₁ Z₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
g₁₁ : Y₁ ⟶ Z₁
g₁₂ : Y₁ ⟶ Z₂
g₂₁ : Y₂ ⟶ Z₁
g₂₂ : Y₂ ⟶ Z₂
⊢ (biprod.inr ≫
        (biprod.fst ≫ f₁₁ ≫ biprod.inl + biprod.fst ≫ f₁₂ ≫ biprod.inr + biprod.snd ≫ f₂₁ ≫ biprod.inl +
            biprod.snd ≫ f₂₂ ≫ biprod.inr) ≫
          (biprod.fst ≫ g₁₁ ≫ biprod.inl + biprod.fst ≫ g₁₂ ≫ biprod.inr + biprod.snd ≫ g₂₁ ≫ biprod.inl +
            biprod.snd ≫ g₂₂ ≫ biprod.inr)) ≫
      biprod.fst =
    (biprod.inr ≫
        (biprod.fst ≫ (f₁₁ ≫ g₁₁ + f₁₂ ≫ g₂₁) ≫ biprod.inl + biprod.fst ≫ (f₁₁ ≫ g₁₂ + f₁₂ ≫ g₂₂) ≫ biprod.inr +
            biprod.snd ≫ (f₂₁ ≫ g₁₁ + f₂₂ ≫ g₂₁) ≫ biprod.inl +
          biprod.snd ≫ (f₂₁ ≫ g₁₂ + f₂₂ ≫ g₂₂) ≫ biprod.inr)) ≫
      biprod.fst

Next tactic:
simp only [add_comp, comp_add, add_comp_assoc, add_zero, zero_add, biprod.inl_fst,
      biprod.inl_snd, biprod.inr_fst, biprod.inr_snd, biprod.inl_fst_assoc, biprod.inl_snd_assoc,
      biprod.inr_fst_assoc, biprod.inr_snd_assoc, comp_zero, zero_comp, Category.assoc]
@[simp]
theorem Biprod.ofComponents_comp {X₁ X₂ Y₁ Y₂ Z₁ Z₂ : C} (f₁₁ : X₁ ⟶ Y₁) (f₁₂ : X₁ ⟶ Y₂)
    (f₂₁ : X₂ ⟶ Y₁) (f₂₂ : X₂ ⟶ Y₂) (g₁₁ : Y₁ ⟶ Z₁) (g₁₂ : Y₁ ⟶ Z₂) (g₂₁ : Y₂ ⟶ Z₁)
    (g₂₂ : Y₂ ⟶ Z₂) :
    Biprod.ofComponents f₁₁ f₁₂ f₂₁ f₂₂ ≫ Biprod.ofComponents g₁₁ g₁₂ g₂₁ g₂₂ =
      Biprod.ofComponents (f₁₁ ≫ g₁₁ + f₁₂ ≫ g₂₁) (f₁₁ ≫ g₁₂ + f₁₂ ≫ g₂₂) (f₂₁ ≫ g₁₁ + f₂₂ ≫ g₂₁)
        (f₂₁ ≫ g₁₂ + f₂₂ ≫ g₂₂) := by
  dsimp [Biprod.ofComponents]
  ext <;>
    

Proof state:
case h₁.h₁
C : Type u
inst✝² : Category.{v, u} C
inst✝¹ : Preadditive C
inst✝ : HasBinaryBiproducts C
X₁✝ X₂✝ Y₁✝ Y₂✝ : C
f₁₁✝ : X₁✝ ⟶ Y₁✝
f₁₂✝ : X₁✝ ⟶ Y₂✝
f₂₁✝ : X₂✝ ⟶ Y₁✝
f₂₂✝ : X₂✝ ⟶ Y₂✝
X₁ X₂ Y₁ Y₂ Z₁ Z₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
g₁₁ : Y₁ ⟶ Z₁
g₁₂ : Y₁ ⟶ Z₂
g₂₁ : Y₂ ⟶ Z₁
g₂₂ : Y₂ ⟶ Z₂
⊢ (biprod.inr ≫
        (biprod.fst ≫ f₁₁ ≫ biprod.inl + biprod.fst ≫ f₁₂ ≫ biprod.inr + biprod.snd ≫ f₂₁ ≫ biprod.inl +
            biprod.snd ≫ f₂₂ ≫ biprod.inr) ≫
          (biprod.fst ≫ g₁₁ ≫ biprod.inl + biprod.fst ≫ g₁₂ ≫ biprod.inr + biprod.snd ≫ g₂₁ ≫ biprod.inl +
            biprod.snd ≫ g₂₂ ≫ biprod.inr)) ≫
      biprod.snd =
    (biprod.inr ≫
        (biprod.fst ≫ (f₁₁ ≫ g₁₁ + f₁₂ ≫ g₂₁) ≫ biprod.inl + biprod.fst ≫ (f₁₁ ≫ g₁₂ + f₁₂ ≫ g₂₂) ≫ biprod.inr +
            biprod.snd ≫ (f₂₁ ≫ g₁₁ + f₂₂ ≫ g₂₁) ≫ biprod.inl +
          biprod.snd ≫ (f₂₁ ≫ g₁₂ + f₂₂ ≫ g₂₂) ≫ biprod.inr)) ≫
      biprod.snd

Next tactic:
simp only [add_comp, comp_add, add_comp_assoc, add_zero, zero_add, biprod.inl_fst,
      biprod.inl_snd, biprod.inr_fst, biprod.inr_snd, biprod.inl_fst_assoc, biprod.inl_snd_assoc,
      biprod.inr_fst_assoc, biprod.inr_snd_assoc, comp_zero, zero_comp, Category.assoc]
/-- If `f` is a morphism `X₁ ⊞ X₂ ⟶ Y₁ ⊞ Y₂` whose `X₁ ⟶ Y₁` entry is an isomorphism,
then we can construct isomorphisms `L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂` and `R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂`
so that `L.hom ≫ g ≫ R.hom` is diagonal (with `X₁ ⟶ Y₁` component still `f`),
via Gaussian elimination.

(This is the version of `Biprod.gaussian` written in terms of components.)
-/
def Biprod.gaussian' [IsIso f₁₁] :
    Σ' (L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂) (R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂) (g₂₂ : X₂ ⟶ Y₂),
      L.hom ≫ Biprod.ofComponents f₁₁ f₁₂ f₂₁ f₂₂ ≫ R.hom = biprod.map f₁₁ g₂₂ :=
  ⟨Biprod.unipotentLower (-f₂₁ ≫ inv f₁₁), Biprod.unipotentUpper (-inv f₁₁ ≫ f₁₂),
    f₂₂ - f₂₁ ≫ inv f₁₁ ≫ f₁₂, by 

Proof state:
C : Type u
inst✝³ : Category.{v, u} C
inst✝² : Preadditive C
inst✝¹ : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
inst✝ : IsIso f₁₁
⊢ (unipotentLower (-f₂₁ ≫ inv f₁₁)).hom ≫ ofComponents f₁₁ f₁₂ f₂₁ f₂₂ ≫ (unipotentUpper (-inv f₁₁ ≫ f₁₂)).hom =
    biprod.map f₁₁ (f₂₂ - f₂₁ ≫ inv f₁₁ ≫ f₁₂)

Next tactic:
ext
/-- If `f` is a morphism `X₁ ⊞ X₂ ⟶ Y₁ ⊞ Y₂` whose `X₁ ⟶ Y₁` entry is an isomorphism,
then we can construct isomorphisms `L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂` and `R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂`
so that `L.hom ≫ g ≫ R.hom` is diagonal (with `X₁ ⟶ Y₁` component still `f`),
via Gaussian elimination.

(This is the version of `Biprod.gaussian` written in terms of components.)
-/
def Biprod.gaussian' [IsIso f₁₁] :
    Σ' (L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂) (R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂) (g₂₂ : X₂ ⟶ Y₂),
      L.hom ≫ Biprod.ofComponents f₁₁ f₁₂ f₂₁ f₂₂ ≫ R.hom = biprod.map f₁₁ g₂₂ :=
  ⟨Biprod.unipotentLower (-f₂₁ ≫ inv f₁₁), Biprod.unipotentUpper (-inv f₁₁ ≫ f₁₂),
    f₂₂ - f₂₁ ≫ inv f₁₁ ≫ f₁₂, by ext <;> 

Proof state:
case h₀.h₀
C : Type u
inst✝³ : Category.{v, u} C
inst✝² : Preadditive C
inst✝¹ : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
inst✝ : IsIso f₁₁
⊢ (biprod.inl ≫
        (unipotentLower (-f₂₁ ≫ inv f₁₁)).hom ≫ ofComponents f₁₁ f₁₂ f₂₁ f₂₂ ≫ (unipotentUpper (-inv f₁₁ ≫ f₁₂)).hom) ≫
      biprod.fst =
    (biprod.inl ≫ biprod.map f₁₁ (f₂₂ - f₂₁ ≫ inv f₁₁ ≫ f₁₂)) ≫ biprod.fst

Next tactic:
simp
/-- If `f` is a morphism `X₁ ⊞ X₂ ⟶ Y₁ ⊞ Y₂` whose `X₁ ⟶ Y₁` entry is an isomorphism,
then we can construct isomorphisms `L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂` and `R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂`
so that `L.hom ≫ g ≫ R.hom` is diagonal (with `X₁ ⟶ Y₁` component still `f`),
via Gaussian elimination.

(This is the version of `Biprod.gaussian` written in terms of components.)
-/
def Biprod.gaussian' [IsIso f₁₁] :
    Σ' (L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂) (R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂) (g₂₂ : X₂ ⟶ Y₂),
      L.hom ≫ Biprod.ofComponents f₁₁ f₁₂ f₂₁ f₂₂ ≫ R.hom = biprod.map f₁₁ g₂₂ :=
  ⟨Biprod.unipotentLower (-f₂₁ ≫ inv f₁₁), Biprod.unipotentUpper (-inv f₁₁ ≫ f₁₂),
    f₂₂ - f₂₁ ≫ inv f₁₁ ≫ f₁₂, by ext <;> 

Proof state:
case h₀.h₁
C : Type u
inst✝³ : Category.{v, u} C
inst✝² : Preadditive C
inst✝¹ : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
inst✝ : IsIso f₁₁
⊢ (biprod.inl ≫
        (unipotentLower (-f₂₁ ≫ inv f₁₁)).hom ≫ ofComponents f₁₁ f₁₂ f₂₁ f₂₂ ≫ (unipotentUpper (-inv f₁₁ ≫ f₁₂)).hom) ≫
      biprod.snd =
    (biprod.inl ≫ biprod.map f₁₁ (f₂₂ - f₂₁ ≫ inv f₁₁ ≫ f₁₂)) ≫ biprod.snd

Next tactic:
simp
/-- If `f` is a morphism `X₁ ⊞ X₂ ⟶ Y₁ ⊞ Y₂` whose `X₁ ⟶ Y₁` entry is an isomorphism,
then we can construct isomorphisms `L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂` and `R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂`
so that `L.hom ≫ g ≫ R.hom` is diagonal (with `X₁ ⟶ Y₁` component still `f`),
via Gaussian elimination.

(This is the version of `Biprod.gaussian` written in terms of components.)
-/
def Biprod.gaussian' [IsIso f₁₁] :
    Σ' (L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂) (R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂) (g₂₂ : X₂ ⟶ Y₂),
      L.hom ≫ Biprod.ofComponents f₁₁ f₁₂ f₂₁ f₂₂ ≫ R.hom = biprod.map f₁₁ g₂₂ :=
  ⟨Biprod.unipotentLower (-f₂₁ ≫ inv f₁₁), Biprod.unipotentUpper (-inv f₁₁ ≫ f₁₂),
    f₂₂ - f₂₁ ≫ inv f₁₁ ≫ f₁₂, by ext <;> 

Proof state:
case h₁.h₀
C : Type u
inst✝³ : Category.{v, u} C
inst✝² : Preadditive C
inst✝¹ : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
inst✝ : IsIso f₁₁
⊢ (biprod.inr ≫
        (unipotentLower (-f₂₁ ≫ inv f₁₁)).hom ≫ ofComponents f₁₁ f₁₂ f₂₁ f₂₂ ≫ (unipotentUpper (-inv f₁₁ ≫ f₁₂)).hom) ≫
      biprod.fst =
    (biprod.inr ≫ biprod.map f₁₁ (f₂₂ - f₂₁ ≫ inv f₁₁ ≫ f₁₂)) ≫ biprod.fst

Next tactic:
simp
/-- If `f` is a morphism `X₁ ⊞ X₂ ⟶ Y₁ ⊞ Y₂` whose `X₁ ⟶ Y₁` entry is an isomorphism,
then we can construct isomorphisms `L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂` and `R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂`
so that `L.hom ≫ g ≫ R.hom` is diagonal (with `X₁ ⟶ Y₁` component still `f`),
via Gaussian elimination.

(This is the version of `Biprod.gaussian` written in terms of components.)
-/
def Biprod.gaussian' [IsIso f₁₁] :
    Σ' (L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂) (R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂) (g₂₂ : X₂ ⟶ Y₂),
      L.hom ≫ Biprod.ofComponents f₁₁ f₁₂ f₂₁ f₂₂ ≫ R.hom = biprod.map f₁₁ g₂₂ :=
  ⟨Biprod.unipotentLower (-f₂₁ ≫ inv f₁₁), Biprod.unipotentUpper (-inv f₁₁ ≫ f₁₂),
    f₂₂ - f₂₁ ≫ inv f₁₁ ≫ f₁₂, by ext <;> 

Proof state:
case h₁.h₁
C : Type u
inst✝³ : Category.{v, u} C
inst✝² : Preadditive C
inst✝¹ : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
inst✝ : IsIso f₁₁
⊢ (biprod.inr ≫
        (unipotentLower (-f₂₁ ≫ inv f₁₁)).hom ≫ ofComponents f₁₁ f₁₂ f₂₁ f₂₂ ≫ (unipotentUpper (-inv f₁₁ ≫ f₁₂)).hom) ≫
      biprod.snd =
    (biprod.inr ≫ biprod.map f₁₁ (f₂₂ - f₂₁ ≫ inv f₁₁ ≫ f₁₂)) ≫ biprod.snd

Next tactic:
simp
/-- If `f` is a morphism `X₁ ⊞ X₂ ⟶ Y₁ ⊞ Y₂` whose `X₁ ⟶ Y₁` entry is an isomorphism,
then we can construct isomorphisms `L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂` and `R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂`
so that `L.hom ≫ g ≫ R.hom` is diagonal (with `X₁ ⟶ Y₁` component still `f`),
via Gaussian elimination.

(This is the version of `Biprod.gaussian` written in terms of components.)
-/
def Biprod.gaussian' [IsIso f₁₁] :
    Σ' (L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂) (R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂) (g₂₂ : X₂ ⟶ Y₂),
      L.hom ≫ Biprod.ofComponents f₁₁ f₁₂ f₂₁ f₂₂ ≫ R.hom = biprod.map f₁₁ g₂₂ :=
  ⟨Biprod.unipotentLower (-f₂₁ ≫ inv f₁₁), Biprod.unipotentUpper (-inv f₁₁ ≫ f₁₂),
    f₂₂ - f₂₁ ≫ inv f₁₁ ≫ f₁₂, by ext <;> simp; 

Proof state:
case h₁.h₁
C : Type u
inst✝³ : Category.{v, u} C
inst✝² : Preadditive C
inst✝¹ : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
inst✝ : IsIso f₁₁
⊢ -f₂₁ ≫ inv f₁₁ ≫ f₁₂ + f₂₂ = f₂₂ - f₂₁ ≫ inv f₁₁ ≫ f₁₂

Next tactic:
abel
/-- If `f` is a morphism `X₁ ⊞ X₂ ⟶ Y₁ ⊞ Y₂` whose `X₁ ⟶ Y₁` entry is an isomorphism,
then we can construct isomorphisms `L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂` and `R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂`
so that `L.hom ≫ g ≫ R.hom` is diagonal (with `X₁ ⟶ Y₁` component still `f`),
via Gaussian elimination.
-/
def Biprod.gaussian (f : X₁ ⊞ X₂ ⟶ Y₁ ⊞ Y₂) [IsIso (biprod.inl ≫ f ≫ biprod.fst)] :
    Σ' (L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂) (R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂) (g₂₂ : X₂ ⟶ Y₂),
      L.hom ≫ f ≫ R.hom = biprod.map (biprod.inl ≫ f ≫ biprod.fst) g₂₂ := by
  

Proof state:
C : Type u
inst✝³ : Category.{v, u} C
inst✝² : Preadditive C
inst✝¹ : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
f : X₁ ⊞ X₂ ⟶ Y₁ ⊞ Y₂
inst✝ : IsIso (biprod.inl ≫ f ≫ biprod.fst)
⊢ (L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂) ×'
    (R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂) ×' (g₂₂ : X₂ ⟶ Y₂) ×' L.hom ≫ f ≫ R.hom = biprod.map (biprod.inl ≫ f ≫ biprod.fst) g₂₂

Next tactic:
let this :=
    Biprod.gaussian' (biprod.inl ≫ f ≫ biprod.fst) (biprod.inl ≫ f ≫ biprod.snd)
      (biprod.inr ≫ f ≫ biprod.fst) (biprod.inr ≫ f ≫ biprod.snd)
/-- If `f` is a morphism `X₁ ⊞ X₂ ⟶ Y₁ ⊞ Y₂` whose `X₁ ⟶ Y₁` entry is an isomorphism,
then we can construct isomorphisms `L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂` and `R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂`
so that `L.hom ≫ g ≫ R.hom` is diagonal (with `X₁ ⟶ Y₁` component still `f`),
via Gaussian elimination.
-/
def Biprod.gaussian (f : X₁ ⊞ X₂ ⟶ Y₁ ⊞ Y₂) [IsIso (biprod.inl ≫ f ≫ biprod.fst)] :
    Σ' (L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂) (R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂) (g₂₂ : X₂ ⟶ Y₂),
      L.hom ≫ f ≫ R.hom = biprod.map (biprod.inl ≫ f ≫ biprod.fst) g₂₂ := by
  let this :=
    Biprod.gaussian' (biprod.inl ≫ f ≫ biprod.fst) (biprod.inl ≫ f ≫ biprod.snd)
      (biprod.inr ≫ f ≫ biprod.fst) (biprod.inr ≫ f ≫ biprod.snd)
  

Proof state:
C : Type u
inst✝³ : Category.{v, u} C
inst✝² : Preadditive C
inst✝¹ : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
f : X₁ ⊞ X₂ ⟶ Y₁ ⊞ Y₂
inst✝ : IsIso (biprod.inl ≫ f ≫ biprod.fst)
this : (L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂) ×'
  (R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂) ×'
    (g₂₂ : X₂ ⟶ Y₂) ×'
      L.hom ≫
          ofComponents (biprod.inl ≫ f ≫ biprod.fst) (biprod.inl ≫ f ≫ biprod.snd) (biprod.inr ≫ f ≫ biprod.fst)
              (biprod.inr ≫ f ≫ biprod.snd) ≫
            R.hom =
        biprod.map (biprod.inl ≫ f ≫ biprod.fst) g₂₂ :=
  gaussian' (biprod.inl ≫ f ≫ biprod.fst) (biprod.inl ≫ f ≫ biprod.snd) (biprod.inr ≫ f ≫ biprod.fst)
    (biprod.inr ≫ f ≫ biprod.snd)
⊢ (L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂) ×'
    (R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂) ×' (g₂₂ : X₂ ⟶ Y₂) ×' L.hom ≫ f ≫ R.hom = biprod.map (biprod.inl ≫ f ≫ biprod.fst) g₂₂

Next tactic:
rwa [Biprod.ofComponents_eq] at this
/-- If `X₁ ⊞ X₂ ≅ Y₁ ⊞ Y₂` via a two-by-two matrix whose `X₁ ⟶ Y₁` entry is an isomorphism,
then we can construct an isomorphism `X₂ ≅ Y₂`, via Gaussian elimination.
-/
def Biprod.isoElim' [IsIso f₁₁] [IsIso (Biprod.ofComponents f₁₁ f₁₂ f₂₁ f₂₂)] : X₂ ≅ Y₂ := by
  

Proof state:
C : Type u
inst✝⁴ : Category.{v, u} C
inst✝³ : Preadditive C
inst✝² : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
inst✝¹ : IsIso f₁₁
inst✝ : IsIso (ofComponents f₁₁ f₁₂ f₂₁ f₂₂)
⊢ X₂ ≅ Y₂

Next tactic:
obtain ⟨L, R, g, w⟩ := Biprod.gaussian' f₁₁ f₁₂ f₂₁ f₂₂
/-- If `X₁ ⊞ X₂ ≅ Y₁ ⊞ Y₂` via a two-by-two matrix whose `X₁ ⟶ Y₁` entry is an isomorphism,
then we can construct an isomorphism `X₂ ≅ Y₂`, via Gaussian elimination.
-/
def Biprod.isoElim' [IsIso f₁₁] [IsIso (Biprod.ofComponents f₁₁ f₁₂ f₂₁ f₂₂)] : X₂ ≅ Y₂ := by
  obtain ⟨L, R, g, w⟩ := Biprod.gaussian' f₁₁ f₁₂ f₂₁ f₂₂
  

Proof state:
case mk.mk.mk
C : Type u
inst✝⁴ : Category.{v, u} C
inst✝³ : Preadditive C
inst✝² : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
inst✝¹ : IsIso f₁₁
inst✝ : IsIso (ofComponents f₁₁ f₁₂ f₂₁ f₂₂)
L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂
R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂
g : X₂ ⟶ Y₂
w : L.hom ≫ ofComponents f₁₁ f₁₂ f₂₁ f₂₂ ≫ R.hom = biprod.map f₁₁ g
⊢ X₂ ≅ Y₂

Next tactic:
letI : IsIso (biprod.map f₁₁ g) := by
    rw [← w]
    infer_instance
/-- If `X₁ ⊞ X₂ ≅ Y₁ ⊞ Y₂` via a two-by-two matrix whose `X₁ ⟶ Y₁` entry is an isomorphism,
then we can construct an isomorphism `X₂ ≅ Y₂`, via Gaussian elimination.
-/
def Biprod.isoElim' [IsIso f₁₁] [IsIso (Biprod.ofComponents f₁₁ f₁₂ f₂₁ f₂₂)] : X₂ ≅ Y₂ := by
  obtain ⟨L, R, g, w⟩ := Biprod.gaussian' f₁₁ f₁₂ f₂₁ f₂₂
  letI : IsIso (biprod.map f₁₁ g) := by
    

Proof state:
C : Type u
inst✝⁴ : Category.{v, u} C
inst✝³ : Preadditive C
inst✝² : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
inst✝¹ : IsIso f₁₁
inst✝ : IsIso (ofComponents f₁₁ f₁₂ f₂₁ f₂₂)
L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂
R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂
g : X₂ ⟶ Y₂
w : L.hom ≫ ofComponents f₁₁ f₁₂ f₂₁ f₂₂ ≫ R.hom = biprod.map f₁₁ g
⊢ IsIso (biprod.map f₁₁ g)

Next tactic:
rw [← w]
/-- If `X₁ ⊞ X₂ ≅ Y₁ ⊞ Y₂` via a two-by-two matrix whose `X₁ ⟶ Y₁` entry is an isomorphism,
then we can construct an isomorphism `X₂ ≅ Y₂`, via Gaussian elimination.
-/
def Biprod.isoElim' [IsIso f₁₁] [IsIso (Biprod.ofComponents f₁₁ f₁₂ f₂₁ f₂₂)] : X₂ ≅ Y₂ := by
  obtain ⟨L, R, g, w⟩ := Biprod.gaussian' f₁₁ f₁₂ f₂₁ f₂₂
  letI : IsIso (biprod.map f₁₁ g) := by
    rw [← w]
    

Proof state:
C : Type u
inst✝⁴ : Category.{v, u} C
inst✝³ : Preadditive C
inst✝² : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
inst✝¹ : IsIso f₁₁
inst✝ : IsIso (ofComponents f₁₁ f₁₂ f₂₁ f₂₂)
L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂
R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂
g : X₂ ⟶ Y₂
w : L.hom ≫ ofComponents f₁₁ f₁₂ f₂₁ f₂₂ ≫ R.hom = biprod.map f₁₁ g
⊢ IsIso (L.hom ≫ ofComponents f₁₁ f₁₂ f₂₁ f₂₂ ≫ R.hom)

Next tactic:
infer_instance
/-- If `X₁ ⊞ X₂ ≅ Y₁ ⊞ Y₂` via a two-by-two matrix whose `X₁ ⟶ Y₁` entry is an isomorphism,
then we can construct an isomorphism `X₂ ≅ Y₂`, via Gaussian elimination.
-/
def Biprod.isoElim' [IsIso f₁₁] [IsIso (Biprod.ofComponents f₁₁ f₁₂ f₂₁ f₂₂)] : X₂ ≅ Y₂ := by
  obtain ⟨L, R, g, w⟩ := Biprod.gaussian' f₁₁ f₁₂ f₂₁ f₂₂
  letI : IsIso (biprod.map f₁₁ g) := by
    rw [← w]
    infer_instance
  

Proof state:
case mk.mk.mk
C : Type u
inst✝⁴ : Category.{v, u} C
inst✝³ : Preadditive C
inst✝² : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
inst✝¹ : IsIso f₁₁
inst✝ : IsIso (ofComponents f₁₁ f₁₂ f₂₁ f₂₂)
L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂
R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂
g : X₂ ⟶ Y₂
w : L.hom ≫ ofComponents f₁₁ f₁₂ f₂₁ f₂₂ ≫ R.hom = biprod.map f₁₁ g
this : IsIso (biprod.map f₁₁ g) := Eq.mpr (id (w.symm ▸ Eq.refl (IsIso (biprod.map f₁₁ g)))) inferInstance
⊢ X₂ ≅ Y₂

Next tactic:
letI : IsIso g := isIso_right_of_isIso_biprod_map f₁₁ g
/-- If `X₁ ⊞ X₂ ≅ Y₁ ⊞ Y₂` via a two-by-two matrix whose `X₁ ⟶ Y₁` entry is an isomorphism,
then we can construct an isomorphism `X₂ ≅ Y₂`, via Gaussian elimination.
-/
def Biprod.isoElim' [IsIso f₁₁] [IsIso (Biprod.ofComponents f₁₁ f₁₂ f₂₁ f₂₂)] : X₂ ≅ Y₂ := by
  obtain ⟨L, R, g, w⟩ := Biprod.gaussian' f₁₁ f₁₂ f₂₁ f₂₂
  letI : IsIso (biprod.map f₁₁ g) := by
    rw [← w]
    infer_instance
  letI : IsIso g := isIso_right_of_isIso_biprod_map f₁₁ g
  

Proof state:
case mk.mk.mk
C : Type u
inst✝⁴ : Category.{v, u} C
inst✝³ : Preadditive C
inst✝² : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
inst✝¹ : IsIso f₁₁
inst✝ : IsIso (ofComponents f₁₁ f₁₂ f₂₁ f₂₂)
L : X₁ ⊞ X₂ ≅ X₁ ⊞ X₂
R : Y₁ ⊞ Y₂ ≅ Y₁ ⊞ Y₂
g : X₂ ⟶ Y₂
w : L.hom ≫ ofComponents f₁₁ f₁₂ f₂₁ f₂₂ ≫ R.hom = biprod.map f₁₁ g
this✝ : IsIso (biprod.map f₁₁ g) := Eq.mpr (id (w.symm ▸ Eq.refl (IsIso (biprod.map f₁₁ g)))) inferInstance
this : IsIso g := isIso_right_of_isIso_biprod_map f₁₁ g
⊢ X₂ ≅ Y₂

Next tactic:
exact asIso g
/-- If `f` is an isomorphism `X₁ ⊞ X₂ ≅ Y₁ ⊞ Y₂` whose `X₁ ⟶ Y₁` entry is an isomorphism,
then we can construct an isomorphism `X₂ ≅ Y₂`, via Gaussian elimination.
-/
def Biprod.isoElim (f : X₁ ⊞ X₂ ≅ Y₁ ⊞ Y₂) [IsIso (biprod.inl ≫ f.hom ≫ biprod.fst)] : X₂ ≅ Y₂ :=
  letI :
    IsIso
      (Biprod.ofComponents (biprod.inl ≫ f.hom ≫ biprod.fst) (biprod.inl ≫ f.hom ≫ biprod.snd)
        (biprod.inr ≫ f.hom ≫ biprod.fst) (biprod.inr ≫ f.hom ≫ biprod.snd)) := by
    

Proof state:
C : Type u
inst✝³ : Category.{v, u} C
inst✝² : Preadditive C
inst✝¹ : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
f : X₁ ⊞ X₂ ≅ Y₁ ⊞ Y₂
inst✝ : IsIso (biprod.inl ≫ f.hom ≫ biprod.fst)
⊢ IsIso
    (ofComponents (biprod.inl ≫ f.hom ≫ biprod.fst) (biprod.inl ≫ f.hom ≫ biprod.snd) (biprod.inr ≫ f.hom ≫ biprod.fst)
      (biprod.inr ≫ f.hom ≫ biprod.snd))

Next tactic:
simp only [Biprod.ofComponents_eq]
/-- If `f` is an isomorphism `X₁ ⊞ X₂ ≅ Y₁ ⊞ Y₂` whose `X₁ ⟶ Y₁` entry is an isomorphism,
then we can construct an isomorphism `X₂ ≅ Y₂`, via Gaussian elimination.
-/
def Biprod.isoElim (f : X₁ ⊞ X₂ ≅ Y₁ ⊞ Y₂) [IsIso (biprod.inl ≫ f.hom ≫ biprod.fst)] : X₂ ≅ Y₂ :=
  letI :
    IsIso
      (Biprod.ofComponents (biprod.inl ≫ f.hom ≫ biprod.fst) (biprod.inl ≫ f.hom ≫ biprod.snd)
        (biprod.inr ≫ f.hom ≫ biprod.fst) (biprod.inr ≫ f.hom ≫ biprod.snd)) := by
    simp only [Biprod.ofComponents_eq]
    

Proof state:
C : Type u
inst✝³ : Category.{v, u} C
inst✝² : Preadditive C
inst✝¹ : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
f : X₁ ⊞ X₂ ≅ Y₁ ⊞ Y₂
inst✝ : IsIso (biprod.inl ≫ f.hom ≫ biprod.fst)
⊢ IsIso f.hom

Next tactic:
infer_instance
theorem Biprod.column_nonzero_of_iso {W X Y Z : C} (f : W ⊞ X ⟶ Y ⊞ Z) [IsIso f] :
    𝟙 W = 0 ∨ biprod.inl ≫ f ≫ biprod.fst ≠ 0 ∨ biprod.inl ≫ f ≫ biprod.snd ≠ 0 := by
  

Proof state:
C : Type u
inst✝³ : Category.{v, u} C
inst✝² : Preadditive C
inst✝¹ : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
W X Y Z : C
f : W ⊞ X ⟶ Y ⊞ Z
inst✝ : IsIso f
⊢ 𝟙 W = 0 ∨ biprod.inl ≫ f ≫ biprod.fst ≠ 0 ∨ biprod.inl ≫ f ≫ biprod.snd ≠ 0

Next tactic:
by_contra! h
theorem Biprod.column_nonzero_of_iso {W X Y Z : C} (f : W ⊞ X ⟶ Y ⊞ Z) [IsIso f] :
    𝟙 W = 0 ∨ biprod.inl ≫ f ≫ biprod.fst ≠ 0 ∨ biprod.inl ≫ f ≫ biprod.snd ≠ 0 := by
  by_contra! h
  

Proof state:
C : Type u
inst✝³ : Category.{v, u} C
inst✝² : Preadditive C
inst✝¹ : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
W X Y Z : C
f : W ⊞ X ⟶ Y ⊞ Z
inst✝ : IsIso f
h : 𝟙 W ≠ 0 ∧ biprod.inl ≫ f ≫ biprod.fst = 0 ∧ biprod.inl ≫ f ≫ biprod.snd = 0
⊢ False

Next tactic:
rcases h with ⟨nz, a₁, a₂⟩
theorem Biprod.column_nonzero_of_iso {W X Y Z : C} (f : W ⊞ X ⟶ Y ⊞ Z) [IsIso f] :
    𝟙 W = 0 ∨ biprod.inl ≫ f ≫ biprod.fst ≠ 0 ∨ biprod.inl ≫ f ≫ biprod.snd ≠ 0 := by
  by_contra! h
  rcases h with ⟨nz, a₁, a₂⟩
  

Proof state:
case intro.intro
C : Type u
inst✝³ : Category.{v, u} C
inst✝² : Preadditive C
inst✝¹ : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
W X Y Z : C
f : W ⊞ X ⟶ Y ⊞ Z
inst✝ : IsIso f
nz : 𝟙 W ≠ 0
a₁ : biprod.inl ≫ f ≫ biprod.fst = 0
a₂ : biprod.inl ≫ f ≫ biprod.snd = 0
⊢ False

Next tactic:
set x := biprod.inl ≫ f ≫ inv f ≫ biprod.fst
theorem Biprod.column_nonzero_of_iso {W X Y Z : C} (f : W ⊞ X ⟶ Y ⊞ Z) [IsIso f] :
    𝟙 W = 0 ∨ biprod.inl ≫ f ≫ biprod.fst ≠ 0 ∨ biprod.inl ≫ f ≫ biprod.snd ≠ 0 := by
  by_contra! h
  rcases h with ⟨nz, a₁, a₂⟩
  set x := biprod.inl ≫ f ≫ inv f ≫ biprod.fst
  

Proof state:
case intro.intro
C : Type u
inst✝³ : Category.{v, u} C
inst✝² : Preadditive C
inst✝¹ : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
W X Y Z : C
f : W ⊞ X ⟶ Y ⊞ Z
inst✝ : IsIso f
nz : 𝟙 W ≠ 0
a₁ : biprod.inl ≫ f ≫ biprod.fst = 0
a₂ : biprod.inl ≫ f ≫ biprod.snd = 0
x : W ⟶ W := biprod.inl ≫ f ≫ inv f ≫ biprod.fst
⊢ False

Next tactic:
have h₁ : x = 𝟙 W := by simp
theorem Biprod.column_nonzero_of_iso {W X Y Z : C} (f : W ⊞ X ⟶ Y ⊞ Z) [IsIso f] :
    𝟙 W = 0 ∨ biprod.inl ≫ f ≫ biprod.fst ≠ 0 ∨ biprod.inl ≫ f ≫ biprod.snd ≠ 0 := by
  by_contra! h
  rcases h with ⟨nz, a₁, a₂⟩
  set x := biprod.inl ≫ f ≫ inv f ≫ biprod.fst
  have h₁ : x = 𝟙 W := by 

Proof state:
C : Type u
inst✝³ : Category.{v, u} C
inst✝² : Preadditive C
inst✝¹ : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
W X Y Z : C
f : W ⊞ X ⟶ Y ⊞ Z
inst✝ : IsIso f
nz : 𝟙 W ≠ 0
a₁ : biprod.inl ≫ f ≫ biprod.fst = 0
a₂ : biprod.inl ≫ f ≫ biprod.snd = 0
x : W ⟶ W := biprod.inl ≫ f ≫ inv f ≫ biprod.fst
⊢ x = 𝟙 W

Next tactic:
simp
theorem Biprod.column_nonzero_of_iso {W X Y Z : C} (f : W ⊞ X ⟶ Y ⊞ Z) [IsIso f] :
    𝟙 W = 0 ∨ biprod.inl ≫ f ≫ biprod.fst ≠ 0 ∨ biprod.inl ≫ f ≫ biprod.snd ≠ 0 := by
  by_contra! h
  rcases h with ⟨nz, a₁, a₂⟩
  set x := biprod.inl ≫ f ≫ inv f ≫ biprod.fst
  have h₁ : x = 𝟙 W := by simp
  

Proof state:
case intro.intro
C : Type u
inst✝³ : Category.{v, u} C
inst✝² : Preadditive C
inst✝¹ : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
W X Y Z : C
f : W ⊞ X ⟶ Y ⊞ Z
inst✝ : IsIso f
nz : 𝟙 W ≠ 0
a₁ : biprod.inl ≫ f ≫ biprod.fst = 0
a₂ : biprod.inl ≫ f ≫ biprod.snd = 0
x : W ⟶ W := biprod.inl ≫ f ≫ inv f ≫ biprod.fst
h₁ : x = 𝟙 W
⊢ False

Next tactic:
have h₀ : x = 0 := by
    dsimp
    rw [← Category.id_comp (inv f), Category.assoc, ← biprod.total]
    conv_lhs =>
      slice 2 3
      rw [comp_add]
    simp only [Category.assoc]
    rw [comp_add_assoc, add_comp]
    conv_lhs =>
      congr
      next => skip
      slice 1 3
      rw [a₂]
    simp only [zero_comp, add_zero]
    conv_lhs =>
      slice 1 3
      rw [a₁]
    simp only [zero_comp]
theorem Biprod.column_nonzero_of_iso {W X Y Z : C} (f : W ⊞ X ⟶ Y ⊞ Z) [IsIso f] :
    𝟙 W = 0 ∨ biprod.inl ≫ f ≫ biprod.fst ≠ 0 ∨ biprod.inl ≫ f ≫ biprod.snd ≠ 0 := by
  by_contra! h
  rcases h with ⟨nz, a₁, a₂⟩
  set x := biprod.inl ≫ f ≫ inv f ≫ biprod.fst
  have h₁ : x = 𝟙 W := by simp
  have h₀ : x = 0 := by
    

Proof state:
C : Type u
inst✝³ : Category.{v, u} C
inst✝² : Preadditive C
inst✝¹ : HasBinaryBiproducts C
X₁ X₂ Y₁ Y₂ : C
f₁₁ : X₁ ⟶ Y₁
f₁₂ : X₁ ⟶ Y₂
f₂₁ : X₂ ⟶ Y₁
f₂₂ : X₂ ⟶ Y₂
W X Y Z : C
f : W ⊞ X ⟶ Y ⊞ Z
inst✝ : IsIso f
nz : 𝟙 W ≠ 0
a₁ : biprod.inl ≫ f ≫ biprod.fst = 0
a₂ : biprod.inl ≫ f ≫ biprod.snd = 0
x : W ⟶ W := biprod.inl ≫ f ≫ inv f ≫ biprod.fst
h₁ : x = 𝟙 W
⊢ x = 0

Next tactic:
dsimp