Theorem: CategoryTheory.ShortComplex.LeftHomologyData.ofAbelian_K
File: Mathlib/Algebra/Homology/ShortComplex/Abelian.lean

Proof steps:
state_before: C : Type u
inst✝¹ : Category.{v, u} C
inst✝ : Abelian C
S : ShortComplex C
⊢ S.LeftHomologyData
state_after: C : Type u
inst✝¹ : Category.{v, u} C
inst✝ : Abelian C
S : ShortComplex C
γ : kernel S.g ⟶ cokernel S.f := kernel.ι S.g ≫ cokernel.π S.f
⊢ S.LeftHomologyData
tactic: let γ := kernel.ι S.g ≫ cokernel.π S.f
state_before: C : Type u
inst✝¹ : Category.{v, u} C
inst✝ : Abelian C
S : ShortComplex C
γ : kernel S.g ⟶ cokernel S.f := kernel.ι S.g ≫ cokernel.π S.f
⊢ S.LeftHomologyData
state_after: C : Type u
inst✝¹ : Category.{v, u} C
inst✝ : Abelian C
S : ShortComplex C
γ : kernel S.g ⟶ cokernel S.f := kernel.ι S.g ≫ cokernel.π S.f
f' : S.X₁ ⟶ kernel S.g := kernel.lift S.g S.f ⋯
⊢ S.LeftHomologyData
tactic: let f' := kernel.lift S.g S.f S.zero
state_before: C : Type u
inst✝¹ : Category.{v, u} C
inst✝ : Abelian C
S : ShortComplex C
γ : kernel S.g ⟶ cokernel S.f := kernel.ι S.g ≫ cokernel.π S.f
f' : S.X₁ ⟶ kernel S.g := kernel.lift S.g S.f ⋯
⊢ S.LeftHomologyData
state_after: C : Type u
inst✝¹ : Category.{v, u} C
inst✝ : Abelian C
S : ShortComplex C
γ : kernel S.g ⟶ cokernel S.f := kernel.ι S.g ≫ cokernel.π S.f
f' : S.X₁ ⟶ kernel S.g := kernel.lift S.g S.f ⋯
hf' : f' = kernel.lift γ f' ⋯ ≫ kernel.ι γ
⊢ S.LeftHomologyData
tactic: have hf' : f' = kernel.lift γ f' (by simp [γ, f']) ≫ kernel.ι γ := by rw [kernel.lift_ι]
state_before: C : Type u
inst✝¹ : Category.{v, u} C
inst✝ : Abelian C
S : ShortComplex C
γ : kernel S.g ⟶ cokernel S.f := kernel.ι S.g ≫ cokernel.π S.f
f' : S.X₁ ⟶ kernel S.g := kernel.lift S.g S.f ⋯
hf' : f' = kernel.lift γ f' ⋯ ≫ kernel.ι γ
⊢ S.LeftHomologyData
state_after: C : Type u
inst✝¹ : Category.{v, u} C
inst✝ : Abelian C
S : ShortComplex C
γ : kernel S.g ⟶ cokernel S.f := kernel.ι S.g ≫ cokernel.π S.f
f' : S.X₁ ⟶ kernel S.g := kernel.lift S.g S.f ⋯
hf' : f' = kernel.lift γ f' ⋯ ≫ kernel.ι γ
wπ : f' ≫ cokernel.π (kernel.ι γ) = 0
⊢ S.LeftHomologyData
tactic: have wπ : f' ≫ cokernel.π (kernel.ι γ) = 0 := by
    rw [hf']
    simp only [assoc, cokernel.condition, comp_zero]
state_before: C : Type u
inst✝¹ : Category.{v, u} C
inst✝ : Abelian C
S : ShortComplex C
γ : kernel S.g ⟶ cokernel S.f := kernel.ι S.g ≫ cokernel.π S.f
f' : S.X₁ ⟶ kernel S.g := kernel.lift S.g S.f ⋯
hf' : f' = kernel.lift γ f' ⋯ ≫ kernel.ι γ
wπ : f' ≫ cokernel.π (kernel.ι γ) = 0
⊢ S.LeftHomologyData
state_after: C : Type u
inst✝¹ : Category.{v, u} C
inst✝ : Abelian C
S : ShortComplex C
γ : kernel S.g ⟶ cokernel S.f := kernel.ι S.g ≫ cokernel.π S.f
f' : S.X₁ ⟶ kernel S.g := kernel.lift S.g S.f ⋯
hf' : f' = kernel.lift γ f' ⋯ ≫ kernel.ι γ
wπ : f' ≫ cokernel.π (kernel.ι γ) = 0
e : Abelian.image S.f ≅ kernel γ :=
  S.abelianImageToKernelIsKernel.conePointUniqueUpToIso (limit.isLimit (parallelPair (kernel.ι S.g ≫ cokernel.π S.f) 0))
⊢ S.LeftHomologyData
tactic: let e : Abelian.image S.f ≅ kernel γ :=
    IsLimit.conePointUniqueUpToIso S.abelianImageToKernelIsKernel (limit.isLimit _)
state_before: C : Type u
inst✝¹ : Category.{v, u} C
inst✝ : Abelian C
S : ShortComplex C
γ : kernel S.g ⟶ cokernel S.f := kernel.ι S.g ≫ cokernel.π S.f
f' : S.X₁ ⟶ kernel S.g := kernel.lift S.g S.f ⋯
hf' : f' = kernel.lift γ f' ⋯ ≫ kernel.ι γ
wπ : f' ≫ cokernel.π (kernel.ι γ) = 0
e : Abelian.image S.f ≅ kernel γ :=
  S.abelianImageToKernelIsKernel.conePointUniqueUpToIso (limit.isLimit (parallelPair (kernel.ι S.g ≫ cokernel.π S.f) 0))
⊢ S.LeftHomologyData
state_after: C : Type u
inst✝¹ : Category.{v, u} C
inst✝ : Abelian C
S : ShortComplex C
γ : kernel S.g ⟶ cokernel S.f := kernel.ι S.g ≫ cokernel.π S.f
f' : S.X₁ ⟶ kernel S.g := kernel.lift S.g S.f ⋯
hf' : f' = kernel.lift γ f' ⋯ ≫ kernel.ι γ
wπ : f' ≫ cokernel.π (kernel.ι γ) = 0
e : Abelian.image S.f ≅ kernel γ :=
  S.abelianImageToKernelIsKernel.conePointUniqueUpToIso (limit.isLimit (parallelPair (kernel.ι S.g ≫ cokernel.π S.f) 0))
he : e.hom ≫ kernel.ι γ = S.abelianImageToKernel
⊢ S.LeftHomologyData
tactic: have he : e.hom ≫ kernel.ι γ = S.abelianImageToKernel :=
    IsLimit.conePointUniqueUpToIso_hom_comp _ _ WalkingParallelPair.zero
state_before: C : Type u
inst✝¹ : Category.{v, u} C
inst✝ : Abelian C
S : ShortComplex C
γ : kernel S.g ⟶ cokernel S.f := kernel.ι S.g ≫ cokernel.π S.f
f' : S.X₁ ⟶ kernel S.g := kernel.lift S.g S.f ⋯
hf' : f' = kernel.lift γ f' ⋯ ≫ kernel.ι γ
wπ : f' ≫ cokernel.π (kernel.ι γ) = 0
e : Abelian.image S.f ≅ kernel γ :=
  S.abelianImageToKernelIsKernel.conePointUniqueUpToIso (limit.isLimit (parallelPair (kernel.ι S.g ≫ cokernel.π S.f) 0))
he : e.hom ≫ kernel.ι γ = S.abelianImageToKernel
⊢ S.LeftHomologyData
state_after: C : Type u
inst✝¹ : Category.{v, u} C
inst✝ : Abelian C
S : ShortComplex C
γ : kernel S.g ⟶ cokernel S.f := kernel.ι S.g ≫ cokernel.π S.f
f' : S.X₁ ⟶ kernel S.g := kernel.lift S.g S.f ⋯
hf' : f' = kernel.lift γ f' ⋯ ≫ kernel.ι γ
wπ : f' ≫ cokernel.π (kernel.ι γ) = 0
e : Abelian.image S.f ≅ kernel γ :=
  S.abelianImageToKernelIsKernel.conePointUniqueUpToIso (limit.isLimit (parallelPair (kernel.ι S.g ≫ cokernel.π S.f) 0))
he : e.hom ≫ kernel.ι γ = S.abelianImageToKernel
fac : f' = Abelian.factorThruImage S.f ≫ e.hom ≫ kernel.ι γ
⊢ S.LeftHomologyData
tactic: have fac : f' = Abelian.factorThruImage S.f ≫ e.hom ≫ kernel.ι γ := by
    rw [hf', he]
    simp only [f', kernel.lift_ι, abelianImageToKernel, ← cancel_mono (kernel.ι S.g), assoc]
state_before: C : Type u
inst✝¹ : Category.{v, u} C
inst✝ : Abelian C
S : ShortComplex C
γ : kernel S.g ⟶ cokernel S.f := kernel.ι S.g ≫ cokernel.π S.f
f' : S.X₁ ⟶ kernel S.g := kernel.lift S.g S.f ⋯
hf' : f' = kernel.lift γ f' ⋯ ≫ kernel.ι γ
wπ : f' ≫ cokernel.π (kernel.ι γ) = 0
e : Abelian.image S.f ≅ kernel γ :=
  S.abelianImageToKernelIsKernel.conePointUniqueUpToIso (limit.isLimit (parallelPair (kernel.ι S.g ≫ cokernel.π S.f) 0))
he : e.hom ≫ kernel.ι γ = S.abelianImageToKernel
fac : f' = Abelian.factorThruImage S.f ≫ e.hom ≫ kernel.ι γ
⊢ S.LeftHomologyData
state_after: C : Type u
inst✝¹ : Category.{v, u} C
inst✝ : Abelian C
S : ShortComplex C
γ : kernel S.g ⟶ cokernel S.f := kernel.ι S.g ≫ cokernel.π S.f
f' : S.X₁ ⟶ kernel S.g := kernel.lift S.g S.f ⋯
hf' : f' = kernel.lift γ f' ⋯ ≫ kernel.ι γ
wπ : f' ≫ cokernel.π (kernel.ι γ) = 0
e : Abelian.image S.f ≅ kernel γ :=
  S.abelianImageToKernelIsKernel.conePointUniqueUpToIso (limit.isLimit (parallelPair (kernel.ι S.g ≫ cokernel.π S.f) 0))
he : e.hom ≫ kernel.ι γ = S.abelianImageToKernel
fac : f' = Abelian.factorThruImage S.f ≫ e.hom ≫ kernel.ι γ
hπ : IsColimit (CokernelCofork.ofπ (cokernel.π (kernel.ι γ)) wπ)
⊢ S.LeftHomologyData
tactic: have hπ : IsColimit (CokernelCofork.ofπ _ wπ) :=
    CokernelCofork.IsColimit.ofπ _ _
    (fun x hx => cokernel.desc _ x (by
      simpa only [← cancel_epi e.hom, ← cancel_epi (Abelian.factorThruImage S.f),
        comp_zero, fac, assoc] using hx))
    (fun x hx => cokernel.π_desc _ _ _)
    (fun x hx b hb => coequalizer.hom_ext (by simp only [hb, cokernel.π_desc]))
state_before: C : Type u
inst✝¹ : Category.{v, u} C
inst✝ : Abelian C
S : ShortComplex C
γ : kernel S.g ⟶ cokernel S.f := kernel.ι S.g ≫ cokernel.π S.f
f' : S.X₁ ⟶ kernel S.g := kernel.lift S.g S.f ⋯
hf' : f' = kernel.lift γ f' ⋯ ≫ kernel.ι γ
wπ : f' ≫ cokernel.π (kernel.ι γ) = 0
e : Abelian.image S.f ≅ kernel γ :=
  S.abelianImageToKernelIsKernel.conePointUniqueUpToIso (limit.isLimit (parallelPair (kernel.ι S.g ≫ cokernel.π S.f) 0))
he : e.hom ≫ kernel.ι γ = S.abelianImageToKernel
fac : f' = Abelian.factorThruImage S.f ≫ e.hom ≫ kernel.ι γ
hπ : IsColimit (CokernelCofork.ofπ (cokernel.π (kernel.ι γ)) wπ)
⊢ S.LeftHomologyData
state_after: no goals
tactic: exact
    { K := kernel S.g,
      H := Abelian.coimage (kernel.ι S.g ≫ cokernel.π S.f)
      i := kernel.ι _,
      π := cokernel.π _
      wi := kernel.condition _
      hi := kernelIsKernel _
      wπ := wπ
      hπ := hπ }