-- Mathlib/Analysis/BoxIntegral/UnitPartition.lean
theorem _root_.tendsto_tsum_div_pow_atTop_integral (hF : Continuous F) (hs₁ : IsBounded s)
    (hs₂ : MeasurableSet s) (hs₃ : volume (frontier s) = 0) :
    Tendsto (fun n : ℕ ↦ (∑' x : ↑(s ∩ (n : ℝ)⁻¹ • L), F x) / n ^ card ι)
      atTop (nhds (∫ x in s, F x))

Proof state:
case intro.intro.intro.intro
ι : Type u_1
inst✝ : Fintype ι
s : Set (ι → ℝ)
F : (ι → ℝ) → ℝ
hF : Continuous F
hs₁ : Bornology.IsBounded s
hs₂ : MeasurableSet s
hs₃ : volume (frontier s) = 0
B : Box ι
hB : hasIntegralVertices B
hs₀ : s ≤ ↑B
ε : ℝ
hε : ε > 0
h₁ : ∃ C, ∀ x ∈ Box.Icc B, ‖s.indicator F x‖ ≤ C
h₂ : ∀ᵐ (x : ι → ℝ), ContinuousAt (s.indicator F) x
r : NNReal → (ι → ℝ) → ↑(Set.Ioi 0)
hr₁ : ∀ (c : NNReal), IntegrationParams.Riemann.RCond (r c)
hr₂ :
  ∀ (c : NNReal) (π : TaggedPrepartition B),
    IntegrationParams.Riemann.MemBaseSet B c (r c) π →
      π.IsPartition →
        dist (integralSum (s.indicator F) volume.toBoxAdditive.toSMul π)
            (∫ (x : ι → ℝ) in ↑B, s.indicator F x ∂volume) ≤
          ε / 2
n : ℕ
hn : n ≥ ⌈(↑(r 0 0))⁻¹⌉₊
this : NeZero n
⊢ dist (integralSum (s.indicator F) volume.toBoxAdditive.toSMul (prepartition n B))
      (∫ (x : ι → ℝ) in ↑B, s.indicator F x ∂volume) ≤
    ε / 2

Tactic:
refine hr₂ 0 _ ⟨?_, fun _ ↦ ?_, fun h ↦ ?_, fun h ↦ ?_⟩ (prepartition_isPartition _ hB)

Result:
case intro.intro.intro.intro.refine_1
ι : Type u_1
inst✝ : Fintype ι
s : Set (ι → ℝ)
F : (ι → ℝ) → ℝ
hF : Continuous F
hs₁ : Bornology.IsBounded s
hs₂ : MeasurableSet s
hs₃ : volume (frontier s) = 0
B : Box ι
hB : hasIntegralVertices B
hs₀ : s ≤ ↑B
ε : ℝ
hε : ε > 0
h₁ : ∃ C, ∀ x ∈ Box.Icc B, ‖s.indicator F x‖ ≤ C
h₂ : ∀ᵐ (x : ι → ℝ), ContinuousAt (s.indicator F) x
r : NNReal → (ι → ℝ) → ↑(Set.Ioi 0)
hr₁ : ∀ (c : NNReal), IntegrationParams.Riemann.RCond (r c)
hr₂ :
  ∀ (c : NNReal) (π : TaggedPrepartition B),
    IntegrationParams.Riemann.MemBaseSet B c (r c) π →
      π.IsPartition →
        dist (integralSum (s.indicator F) volume.toBoxAdditive.toSMul π)
            (∫ (x : ι → ℝ) in ↑B, s.indicator F x ∂volume) ≤
          ε / 2
n : ℕ
hn : n ≥ ⌈(↑(r 0 0))⁻¹⌉₊
this : NeZero n
⊢ (prepartition n B).IsSubordinate (r 0)

case intro.intro.intro.intro.refine_2
ι : Type u_1
inst✝ : Fintype ι
s : Set (ι → ℝ)
F : (ι → ℝ) → ℝ
hF : Continuous F
hs₁ : Bornology.IsBounded s
hs₂ : MeasurableSet s
hs₃ : volume (frontier s) = 0
B : Box ι
hB : hasIntegralVertices B
hs₀ : s ≤ ↑B
ε : ℝ
hε : ε > 0
h₁ : ∃ C, ∀ x ∈ Box.Icc B, ‖s.indicator F x‖ ≤ C
h₂ : ∀ᵐ (x : ι → ℝ), ContinuousAt (s.indicator F) x
r : NNReal → (ι → ℝ) → ↑(Set.Ioi 0)
hr₁ : ∀ (c : NNReal), IntegrationParams.Riemann.RCond (r c)
hr₂ :
  ∀ (c : NNReal) (π : TaggedPrepartition B),
    IntegrationParams.Riemann.MemBaseSet B c (r c) π →
      π.IsPartition →
        dist (integralSum (s.indicator F) volume.toBoxAdditive.toSMul π)
            (∫ (x : ι → ℝ) in ↑B, s.indicator F x ∂volume) ≤
          ε / 2
n : ℕ
hn : n ≥ ⌈(↑(r 0 0))⁻¹⌉₊
this : NeZero n
x✝ : IntegrationParams.Riemann.bHenstock = true
⊢ (prepartition n B).IsHenstock

case intro.intro.intro.intro.refine_3
ι : Type u_1
inst✝ : Fintype ι
s : Set (ι → ℝ)
F : (ι → ℝ) → ℝ
hF : Continuous F
hs₁ : Bornology.IsBounded s
hs₂ : MeasurableSet s
hs₃ : volume (frontier s) = 0
B : Box ι
hB : hasIntegralVertices B
hs₀ : s ≤ ↑B
ε : ℝ
hε : ε > 0
h₁ : ∃ C, ∀ x ∈ Box.Icc B, ‖s.indicator F x‖ ≤ C
h₂ : ∀ᵐ (x : ι → ℝ), ContinuousAt (s.indicator F) x
r : NNReal → (ι → ℝ) → ↑(Set.Ioi 0)
hr₁ : ∀ (c : NNReal), IntegrationParams.Riemann.RCond (r c)
hr₂ :
  ∀ (c : NNReal) (π : TaggedPrepartition B),
    IntegrationParams.Riemann.MemBaseSet B c (r c) π →
      π.IsPartition →
        dist (integralSum (s.indicator F) volume.toBoxAdditive.toSMul π)
            (∫ (x : ι → ℝ) in ↑B, s.indicator F x ∂volume) ≤
          ε / 2
n : ℕ
hn : n ≥ ⌈(↑(r 0 0))⁻¹⌉₊
this : NeZero n
h : IntegrationParams.Riemann.bDistortion = true
⊢ (prepartition n B).distortion ≤ 0

case intro.intro.intro.intro.refine_4
ι : Type u_1
inst✝ : Fintype ι
s : Set (ι → ℝ)
F : (ι → ℝ) → ℝ
hF : Continuous F
hs₁ : Bornology.IsBounded s
hs₂ : MeasurableSet s
hs₃ : volume (frontier s) = 0
B : Box ι
hB : hasIntegralVertices B
hs₀ : s ≤ ↑B
ε : ℝ
hε : ε > 0
h₁ : ∃ C, ∀ x ∈ Box.Icc B, ‖s.indicator F x‖ ≤ C
h₂ : ∀ᵐ (x : ι → ℝ), ContinuousAt (s.indicator F) x
r : NNReal → (ι → ℝ) → ↑(Set.Ioi 0)
hr₁ : ∀ (c : NNReal), IntegrationParams.Riemann.RCond (r c)
hr₂ :
  ∀ (c : NNReal) (π : TaggedPrepartition B),
    IntegrationParams.Riemann.MemBaseSet B c (r c) π →
      π.IsPartition →
        dist (integralSum (s.indicator F) volume.toBoxAdditive.toSMul π)
            (∫ (x : ι → ℝ) in ↑B, s.indicator F x ∂volume) ≤
          ε / 2
n : ℕ
hn : n ≥ ⌈(↑(r 0 0))⁻¹⌉₊
this : NeZero n
h : IntegrationParams.Riemann.bDistortion = true
⊢ ∃ π', π'.iUnion = ↑B \ (prepartition n B).iUnion ∧ π'.distortion ≤ 0

Proof state:
case intro.intro
ι : Type u_1
inst✝ : Fintype ι
s : Set (ι → ℝ)
F : (ι → ℝ) → ℝ
hF : Continuous F
hs₁ : Bornology.IsBounded s
hs₂ : MeasurableSet s
hs₃ : volume (frontier s) = 0
B : Box ι
hB : hasIntegralVertices B
hs₀ : s ≤ ↑B
⊢ Tendsto (fun n => (∑' (x : ↑(s ∩ (↑n)⁻¹ • ↑(span ℤ (Set.range ⇑(Pi.basisFun ℝ ι))))), F ↑x) / ↑n ^ card ι) atTop
    (nhds (∫ (x : ι → ℝ) in s, F x))

Tactic:
refine Metric.tendsto_atTop.mpr fun ε hε ↦ ?_

Result:
case intro.intro
ι : Type u_1
inst✝ : Fintype ι
s : Set (ι → ℝ)
F : (ι → ℝ) → ℝ
hF : Continuous F
hs₁ : Bornology.IsBounded s
hs₂ : MeasurableSet s
hs₃ : volume (frontier s) = 0
B : Box ι
hB : hasIntegralVertices B
hs₀ : s ≤ ↑B
ε : ℝ
hε : ε > 0
⊢ ∃ N,
    ∀ n ≥ N,
      dist ((∑' (x : ↑(s ∩ (↑n)⁻¹ • ↑(span ℤ (Set.range ⇑(Pi.basisFun ℝ ι))))), F ↑x) / ↑n ^ card ι)
          (∫ (x : ι → ℝ) in s, F x) <
        ε

Proof state:
case intro.intro.intro.intro.refine_1
ι : Type u_1
inst✝ : Fintype ι
s : Set (ι → ℝ)
F : (ι → ℝ) → ℝ
hF : Continuous F
hs₁ : Bornology.IsBounded s
hs₂ : MeasurableSet s
hs₃ : volume (frontier s) = 0
B : Box ι
hB : hasIntegralVertices B
hs₀ : s ≤ ↑B
ε : ℝ
hε : ε > 0
h₁ : ∃ C, ∀ x ∈ Box.Icc B, ‖s.indicator F x‖ ≤ C
h₂ : ∀ᵐ (x : ι → ℝ), ContinuousAt (s.indicator F) x
r : NNReal → (ι → ℝ) → ↑(Set.Ioi 0)
hr₁ : ∀ (c : NNReal), IntegrationParams.Riemann.RCond (r c)
hr₂ :
  ∀ (c : NNReal) (π : TaggedPrepartition B),
    IntegrationParams.Riemann.MemBaseSet B c (r c) π →
      π.IsPartition →
        dist (integralSum (s.indicator F) volume.toBoxAdditive.toSMul π)
            (∫ (x : ι → ℝ) in ↑B, s.indicator F x ∂volume) ≤
          ε / 2
n : ℕ
hn : n ≥ ⌈(↑(r 0 0))⁻¹⌉₊
this : NeZero n
⊢ (prepartition n B).IsSubordinate fun x => r 0 0

Tactic:
apply prepartition_isSubordinate n B

Result:
case intro.intro.intro.intro.refine_1.hn
ι : Type u_1
inst✝ : Fintype ι
s : Set (ι → ℝ)
F : (ι → ℝ) → ℝ
hF : Continuous F
hs₁ : Bornology.IsBounded s
hs₂ : MeasurableSet s
hs₃ : volume (frontier s) = 0
B : Box ι
hB : hasIntegralVertices B
hs₀ : s ≤ ↑B
ε : ℝ
hε : ε > 0
h₁ : ∃ C, ∀ x ∈ Box.Icc B, ‖s.indicator F x‖ ≤ C
h₂ : ∀ᵐ (x : ι → ℝ), ContinuousAt (s.indicator F) x
r : NNReal → (ι → ℝ) → ↑(Set.Ioi 0)
hr₁ : ∀ (c : NNReal), IntegrationParams.Riemann.RCond (r c)
hr₂ :
  ∀ (c : NNReal) (π : TaggedPrepartition B),
    IntegrationParams.Riemann.MemBaseSet B c (r c) π →
      π.IsPartition →
        dist (integralSum (s.indicator F) volume.toBoxAdditive.toSMul π)
            (∫ (x : ι → ℝ) in ↑B, s.indicator F x ∂volume) ≤
          ε / 2
n : ℕ
hn : n ≥ ⌈(↑(r 0 0))⁻¹⌉₊
this : NeZero n
⊢ 1 / ↑n ≤ ↑(r 0 0)