-- Mathlib/AlgebraicTopology/DoldKan/FunctorGamma.lean
theorem HigherFacesVanish.on_Γ₀_summand_id (K : ChainComplex C ℕ) (n : ℕ) :
    @HigherFacesVanish C _ _ (Γ₀.obj K) _ n (n + 1)
      (((Γ₀.splitting K).cofan _).inj (Splitting.IndexSet.id (op ⦋n + 1⦌)))

Proof state:
C : Type u_1
inst✝² : Category.{u_2, u_1} C
inst✝¹ : Preadditive C
inst✝ : HasFiniteCoproducts C
K : ChainComplex C ℕ
n : ℕ
⊢ HigherFacesVanish (n + 1) (((Γ₀.splitting K).cofan (op ⦋n + 1⦌)).inj (Splitting.IndexSet.id (op ⦋n + 1⦌)))

Tactic:
intro j _

Result:
C : Type u_1
inst✝² : Category.{u_2, u_1} C
inst✝¹ : Preadditive C
inst✝ : HasFiniteCoproducts C
K : ChainComplex C ℕ
n : ℕ
j : Fin (n + 1)
a✝ : n + 1 ≤ ↑j + (n + 1)
⊢ ((Γ₀.splitting K).cofan (op ⦋n + 1⦌)).inj (Splitting.IndexSet.id (op ⦋n + 1⦌)) ≫ (Γ₀.obj K).δ j.succ = 0

Proof state:
C : Type u_1
inst✝² : Category.{u_2, u_1} C
inst✝¹ : Preadditive C
inst✝ : HasFiniteCoproducts C
K : ChainComplex C ℕ
n : ℕ
j : Fin (n + 1)
a✝ : n + 1 ≤ ↑j + (n + 1)
eq :
  ((Γ₀.splitting K).cofan (op ⦋n + 1⦌)).inj (Splitting.IndexSet.id (op ⦋n + 1⦌)) ≫
      (Γ₀.obj K).map (SimplexCategory.δ j.succ).op =
    0
⊢ ((Γ₀.splitting K).cofan (op ⦋n + 1⦌)).inj (Splitting.IndexSet.id (op ⦋n + 1⦌)) ≫ (Γ₀.obj K).δ j.succ = 0

case h₁
C : Type u_1
inst✝² : Category.{u_2, u_1} C
inst✝¹ : Preadditive C
inst✝ : HasFiniteCoproducts C
K : ChainComplex C ℕ
n : ℕ
j : Fin (n + 1)
a✝ : n + 1 ≤ ↑j + (n + 1)
eq :
  ((Γ₀.splitting K).cofan (op ⦋n + 1⦌)).inj (Splitting.IndexSet.id (op ⦋n + 1⦌)) ≫
      (Γ₀.obj K).map (SimplexCategory.δ j.succ).op =
    Γ₀.Obj.Termwise.mapMono K (SimplexCategory.δ j.succ) ≫
      ((Γ₀.splitting K).cofan (op ⦋n⦌)).inj (Splitting.IndexSet.id (op ⦋n⦌))
⊢ ⦋n + 1⦌ ≠ ⦋n⦌

case h₂
C : Type u_1
inst✝² : Category.{u_2, u_1} C
inst✝¹ : Preadditive C
inst✝ : HasFiniteCoproducts C
K : ChainComplex C ℕ
n : ℕ
j : Fin (n + 1)
a✝ : n + 1 ≤ ↑j + (n + 1)
eq :
  ((Γ₀.splitting K).cofan (op ⦋n + 1⦌)).inj (Splitting.IndexSet.id (op ⦋n + 1⦌)) ≫
      (Γ₀.obj K).map (SimplexCategory.δ j.succ).op =
    Γ₀.Obj.Termwise.mapMono K (SimplexCategory.δ j.succ) ≫
      ((Γ₀.splitting K).cofan (op ⦋n⦌)).inj (Splitting.IndexSet.id (op ⦋n⦌))
⊢ ¬Isδ₀ (SimplexCategory.δ j.succ)

Tactic:
rotate_left

Result:
case h₁
C : Type u_1
inst✝² : Category.{u_2, u_1} C
inst✝¹ : Preadditive C
inst✝ : HasFiniteCoproducts C
K : ChainComplex C ℕ
n : ℕ
j : Fin (n + 1)
a✝ : n + 1 ≤ ↑j + (n + 1)
eq :
  ((Γ₀.splitting K).cofan (op ⦋n + 1⦌)).inj (Splitting.IndexSet.id (op ⦋n + 1⦌)) ≫
      (Γ₀.obj K).map (SimplexCategory.δ j.succ).op =
    Γ₀.Obj.Termwise.mapMono K (SimplexCategory.δ j.succ) ≫
      ((Γ₀.splitting K).cofan (op ⦋n⦌)).inj (Splitting.IndexSet.id (op ⦋n⦌))
⊢ ⦋n + 1⦌ ≠ ⦋n⦌

case h₂
C : Type u_1
inst✝² : Category.{u_2, u_1} C
inst✝¹ : Preadditive C
inst✝ : HasFiniteCoproducts C
K : ChainComplex C ℕ
n : ℕ
j : Fin (n + 1)
a✝ : n + 1 ≤ ↑j + (n + 1)
eq :
  ((Γ₀.splitting K).cofan (op ⦋n + 1⦌)).inj (Splitting.IndexSet.id (op ⦋n + 1⦌)) ≫
      (Γ₀.obj K).map (SimplexCategory.δ j.succ).op =
    Γ₀.Obj.Termwise.mapMono K (SimplexCategory.δ j.succ) ≫
      ((Γ₀.splitting K).cofan (op ⦋n⦌)).inj (Splitting.IndexSet.id (op ⦋n⦌))
⊢ ¬Isδ₀ (SimplexCategory.δ j.succ)

C : Type u_1
inst✝² : Category.{u_2, u_1} C
inst✝¹ : Preadditive C
inst✝ : HasFiniteCoproducts C
K : ChainComplex C ℕ
n : ℕ
j : Fin (n + 1)
a✝ : n + 1 ≤ ↑j + (n + 1)
eq :
  ((Γ₀.splitting K).cofan (op ⦋n + 1⦌)).inj (Splitting.IndexSet.id (op ⦋n + 1⦌)) ≫
      (Γ₀.obj K).map (SimplexCategory.δ j.succ).op =
    0
⊢ ((Γ₀.splitting K).cofan (op ⦋n + 1⦌)).inj (Splitting.IndexSet.id (op ⦋n + 1⦌)) ≫ (Γ₀.obj K).δ j.succ = 0

Proof state:
C : Type u_1
inst✝² : Category.{u_2, u_1} C
inst✝¹ : Preadditive C
inst✝ : HasFiniteCoproducts C
K : ChainComplex C ℕ
n : ℕ
j : Fin (n + 1)
a✝ : n + 1 ≤ ↑j + (n + 1)
eq :
  ((Γ₀.splitting K).cofan (op ⦋n + 1⦌)).inj (Splitting.IndexSet.id (op ⦋n + 1⦌)) ≫
      (Γ₀.obj K).map (SimplexCategory.δ j.succ).op =
    Γ₀.Obj.Termwise.mapMono K (SimplexCategory.δ j.succ) ≫
      ((Γ₀.splitting K).cofan (op ⦋n⦌)).inj (Splitting.IndexSet.id (op ⦋n⦌))
h : Isδ₀ (SimplexCategory.δ j.succ)
⊢ j.succ = 0

Tactic:
simpa only [Isδ₀.iff] using h

Result:
no goals

Proof state:
C : Type u_1
inst✝² : Category.{u_2, u_1} C
inst✝¹ : Preadditive C
inst✝ : HasFiniteCoproducts C
K : ChainComplex C ℕ
n : ℕ
j : Fin (n + 1)
a✝ : n + 1 ≤ ↑j + (n + 1)
⊢ ((Γ₀.splitting K).cofan (op ⦋n + 1⦌)).inj (Splitting.IndexSet.id (op ⦋n + 1⦌)) ≫ (Γ₀.obj K).δ j.succ = 0

Tactic:
have eq := Γ₀.Obj.mapMono_on_summand_id K (SimplexCategory.δ j.succ)

Result:
C : Type u_1
inst✝² : Category.{u_2, u_1} C
inst✝¹ : Preadditive C
inst✝ : HasFiniteCoproducts C
K : ChainComplex C ℕ
n : ℕ
j : Fin (n + 1)
a✝ : n + 1 ≤ ↑j + (n + 1)
eq :
  ((Γ₀.splitting K).cofan (op ⦋n + 1⦌)).inj (Splitting.IndexSet.id (op ⦋n + 1⦌)) ≫
      (Γ₀.obj K).map (SimplexCategory.δ j.succ).op =
    Γ₀.Obj.Termwise.mapMono K (SimplexCategory.δ j.succ) ≫
      ((Γ₀.splitting K).cofan (op ⦋n⦌)).inj (Splitting.IndexSet.id (op ⦋n⦌))
⊢ ((Γ₀.splitting K).cofan (op ⦋n + 1⦌)).inj (Splitting.IndexSet.id (op ⦋n + 1⦌)) ≫ (Γ₀.obj K).δ j.succ = 0

Proof state:
C : Type u_1
inst✝² : Category.{u_2, u_1} C
inst✝¹ : Preadditive C
inst✝ : HasFiniteCoproducts C
K : ChainComplex C ℕ
n : ℕ
j : Fin (n + 1)
a✝ : n + 1 ≤ ↑j + (n + 1)
eq :
  ((Γ₀.splitting K).cofan (op ⦋n + 1⦌)).inj (Splitting.IndexSet.id (op ⦋n + 1⦌)) ≫
      (Γ₀.obj K).map (SimplexCategory.δ j.succ).op =
    0
⊢ ((Γ₀.splitting K).cofan (op ⦋n + 1⦌)).inj (Splitting.IndexSet.id (op ⦋n + 1⦌)) ≫ (Γ₀.obj K).δ j.succ = 0

Tactic:
exact eq

Result:
no goals

Proof state:
case h₁
C : Type u_1
inst✝² : Category.{u_2, u_1} C
inst✝¹ : Preadditive C
inst✝ : HasFiniteCoproducts C
K : ChainComplex C ℕ
n : ℕ
j : Fin (n + 1)
a✝ : n + 1 ≤ ↑j + (n + 1)
eq :
  ((Γ₀.splitting K).cofan (op ⦋n + 1⦌)).inj (Splitting.IndexSet.id (op ⦋n + 1⦌)) ≫
      (Γ₀.obj K).map (SimplexCategory.δ j.succ).op =
    Γ₀.Obj.Termwise.mapMono K (SimplexCategory.δ j.succ) ≫
      ((Γ₀.splitting K).cofan (op ⦋n⦌)).inj (Splitting.IndexSet.id (op ⦋n⦌))
h : ⦋n + 1⦌ = ⦋n⦌
⊢ False

Tactic:
exact (Nat.succ_ne_self n) (congr_arg SimplexCategory.len h)

Result:
no goals

Proof state:
case h₁
C : Type u_1
inst✝² : Category.{u_2, u_1} C
inst✝¹ : Preadditive C
inst✝ : HasFiniteCoproducts C
K : ChainComplex C ℕ
n : ℕ
j : Fin (n + 1)
a✝ : n + 1 ≤ ↑j + (n + 1)
eq :
  ((Γ₀.splitting K).cofan (op ⦋n + 1⦌)).inj (Splitting.IndexSet.id (op ⦋n + 1⦌)) ≫
      (Γ₀.obj K).map (SimplexCategory.δ j.succ).op =
    Γ₀.Obj.Termwise.mapMono K (SimplexCategory.δ j.succ) ≫
      ((Γ₀.splitting K).cofan (op ⦋n⦌)).inj (Splitting.IndexSet.id (op ⦋n⦌))
⊢ ⦋n + 1⦌ ≠ ⦋n⦌

Tactic:
intro h

Result:
case h₁
C : Type u_1
inst✝² : Category.{u_2, u_1} C
inst✝¹ : Preadditive C
inst✝ : HasFiniteCoproducts C
K : ChainComplex C ℕ
n : ℕ
j : Fin (n + 1)
a✝ : n + 1 ≤ ↑j + (n + 1)
eq :
  ((Γ₀.splitting K).cofan (op ⦋n + 1⦌)).inj (Splitting.IndexSet.id (op ⦋n + 1⦌)) ≫
      (Γ₀.obj K).map (SimplexCategory.δ j.succ).op =
    Γ₀.Obj.Termwise.mapMono K (SimplexCategory.δ j.succ) ≫
      ((Γ₀.splitting K).cofan (op ⦋n⦌)).inj (Splitting.IndexSet.id (op ⦋n⦌))
h : ⦋n + 1⦌ = ⦋n⦌
⊢ False

Proof state:
case h₂
C : Type u_1
inst✝² : Category.{u_2, u_1} C
inst✝¹ : Preadditive C
inst✝ : HasFiniteCoproducts C
K : ChainComplex C ℕ
n : ℕ
j : Fin (n + 1)
a✝ : n + 1 ≤ ↑j + (n + 1)
eq :
  ((Γ₀.splitting K).cofan (op ⦋n + 1⦌)).inj (Splitting.IndexSet.id (op ⦋n + 1⦌)) ≫
      (Γ₀.obj K).map (SimplexCategory.δ j.succ).op =
    Γ₀.Obj.Termwise.mapMono K (SimplexCategory.δ j.succ) ≫
      ((Γ₀.splitting K).cofan (op ⦋n⦌)).inj (Splitting.IndexSet.id (op ⦋n⦌))
⊢ ¬Isδ₀ (SimplexCategory.δ j.succ)

Tactic:
exact fun h => Fin.succ_ne_zero j (by simpa only [Isδ₀.iff] using h)

Result:
no goals