Module: Mathlib.Probability.Martingale.OptionalStopping

Goal state before:
pp: Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
𝒢 : Filtration ℕ m0
f : ℕ → Ω → ℝ
inst✝ : IsFiniteMeasure μ
hsub : Submartingale f 𝒢 μ
hnonneg : 0 ≤ f
ε : ℝ≥0
n : ℕ
⊢ ENNReal.ofReal
      (∫ (x : Ω) in {ω | ↑ε ≤ (range (n + 1)).sup' ⋯ fun k ↦ f k ω} ∪ {ω | ((range (n + 1)).sup' ⋯ fun k ↦ f k ω) < ↑ε},
        stoppedValue f (fun ω ↦ ↑(hittingBtwn f {y | ↑ε ≤ y} 0 n ω)) x ∂μ) =
    ENNReal.ofReal (∫ (ω : Ω), stoppedValue f (fun ω ↦ ↑(hittingBtwn f {y | ↑ε ≤ y} 0 n ω)) ω ∂μ)

pp: case hst
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
𝒢 : Filtration ℕ m0
f : ℕ → Ω → ℝ
inst✝ : IsFiniteMeasure μ
hsub : Submartingale f 𝒢 μ
hnonneg : 0 ≤ f
ε : ℝ≥0
n : ℕ
⊢ Disjoint {ω | ↑ε ≤ (range (n + 1)).sup' ⋯ fun k ↦ f k ω} {ω | ((range (n + 1)).sup' ⋯ fun k ↦ f k ω) < ↑ε}

pp: case ht
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
𝒢 : Filtration ℕ m0
f : ℕ → Ω → ℝ
inst✝ : IsFiniteMeasure μ
hsub : Submartingale f 𝒢 μ
hnonneg : 0 ≤ f
ε : ℝ≥0
n : ℕ
⊢ MeasurableSet {ω | ((range (n + 1)).sup' ⋯ fun k ↦ f k ω) < ↑ε}

pp: case hfs
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
𝒢 : Filtration ℕ m0
f : ℕ → Ω → ℝ
inst✝ : IsFiniteMeasure μ
hsub : Submartingale f 𝒢 μ
hnonneg : 0 ≤ f
ε : ℝ≥0
n : ℕ
⊢ IntegrableOn (stoppedValue f fun ω ↦ ↑(hittingBtwn f {y | ↑ε ≤ y} 0 n ω))
    {ω | ↑ε ≤ (range (n + 1)).sup' ⋯ fun k ↦ f k ω} μ

pp: case hft
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
𝒢 : Filtration ℕ m0
f : ℕ → Ω → ℝ
inst✝ : IsFiniteMeasure μ
hsub : Submartingale f 𝒢 μ
hnonneg : 0 ≤ f
ε : ℝ≥0
n : ℕ
⊢ IntegrableOn (stoppedValue f fun ω ↦ ↑(hittingBtwn f {y | ↑ε ≤ y} 0 n ω))
    {ω | ((range (n + 1)).sup' ⋯ fun k ↦ f k ω) < ↑ε} μ

pp: case hp
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
𝒢 : Filtration ℕ m0
f : ℕ → Ω → ℝ
inst✝ : IsFiniteMeasure μ
hsub : Submartingale f 𝒢 μ
hnonneg : 0 ≤ f
ε : ℝ≥0
n : ℕ
⊢ 0 ≤
    ∫ (ω : Ω) in {ω | ↑ε ≤ (range (n + 1)).sup' ⋯ fun k ↦ f k ω},
      stoppedValue f (fun ω ↦ ↑(hittingBtwn f {y | ↑ε ≤ y} 0 n ω)) ω ∂μ

pp: case hq
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
𝒢 : Filtration ℕ m0
f : ℕ → Ω → ℝ
inst✝ : IsFiniteMeasure μ
hsub : Submartingale f 𝒢 μ
hnonneg : 0 ≤ f
ε : ℝ≥0
n : ℕ
⊢ 0 ≤
    ∫ (ω : Ω) in {ω | ((range (n + 1)).sup' ⋯ fun k ↦ f k ω) < ↑ε},
      stoppedValue f (fun ω ↦ ↑(hittingBtwn f {y | ↑ε ≤ y} 0 n ω)) ω ∂μ

Tactic:
· rw [← setIntegral_univ (μ := μ)]
        convert! rfl
        ext ω
        change _ ↔ (ε : ℝ) ≤ _ ∨ _ < (ε : ℝ)
        simp only [le_or_gt, Set.mem_univ]

Goal state after:
case hst
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
𝒢 : Filtration ℕ m0
f : ℕ → Ω → ℝ
inst✝ : IsFiniteMeasure μ
hsub : Submartingale f 𝒢 μ
hnonneg : 0 ≤ f
ε : ℝ≥0
n : ℕ
⊢ Disjoint {ω | ↑ε ≤ (range (n + 1)).sup' ⋯ fun k ↦ f k ω} {ω | ((range (n + 1)).sup' ⋯ fun k ↦ f k ω) < ↑ε}

case ht
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
𝒢 : Filtration ℕ m0
f : ℕ → Ω → ℝ
inst✝ : IsFiniteMeasure μ
hsub : Submartingale f 𝒢 μ
hnonneg : 0 ≤ f
ε : ℝ≥0
n : ℕ
⊢ MeasurableSet {ω | ((range (n + 1)).sup' ⋯ fun k ↦ f k ω) < ↑ε}

case hfs
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
𝒢 : Filtration ℕ m0
f : ℕ → Ω → ℝ
inst✝ : IsFiniteMeasure μ
hsub : Submartingale f 𝒢 μ
hnonneg : 0 ≤ f
ε : ℝ≥0
n : ℕ
⊢ IntegrableOn (stoppedValue f fun ω ↦ ↑(hittingBtwn f {y | ↑ε ≤ y} 0 n ω))
    {ω | ↑ε ≤ (range (n + 1)).sup' ⋯ fun k ↦ f k ω} μ

case hft
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
𝒢 : Filtration ℕ m0
f : ℕ → Ω → ℝ
inst✝ : IsFiniteMeasure μ
hsub : Submartingale f 𝒢 μ
hnonneg : 0 ≤ f
ε : ℝ≥0
n : ℕ
⊢ IntegrableOn (stoppedValue f fun ω ↦ ↑(hittingBtwn f {y | ↑ε ≤ y} 0 n ω))
    {ω | ((range (n + 1)).sup' ⋯ fun k ↦ f k ω) < ↑ε} μ

case hp
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
𝒢 : Filtration ℕ m0
f : ℕ → Ω → ℝ
inst✝ : IsFiniteMeasure μ
hsub : Submartingale f 𝒢 μ
hnonneg : 0 ≤ f
ε : ℝ≥0
n : ℕ
⊢ 0 ≤
    ∫ (ω : Ω) in {ω | ↑ε ≤ (range (n + 1)).sup' ⋯ fun k ↦ f k ω},
      stoppedValue f (fun ω ↦ ↑(hittingBtwn f {y | ↑ε ≤ y} 0 n ω)) ω ∂μ

case hq
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
𝒢 : Filtration ℕ m0
f : ℕ → Ω → ℝ
inst✝ : IsFiniteMeasure μ
hsub : Submartingale f 𝒢 μ
hnonneg : 0 ≤ f
ε : ℝ≥0
n : ℕ
⊢ 0 ≤
    ∫ (ω : Ω) in {ω | ((range (n + 1)).sup' ⋯ fun k ↦ f k ω) < ↑ε},
      stoppedValue f (fun ω ↦ ↑(hittingBtwn f {y | ↑ε ≤ y} 0 n ω)) ω ∂μ