Module: Mathlib.Analysis.BoxIntegral.Basic

Goal state before:
pp: case refine_1.inr
ι : Type u
E : Type v
F : Type w
inst✝⁴ : NormedAddCommGroup E
inst✝³ : NormedSpace ℝ E
inst✝² : NormedAddCommGroup F
inst✝¹ : NormedSpace ℝ F
I : Box ι
inst✝ : Fintype ι
l : IntegrationParams
f : (ι → ℝ) → E
vol : ι →ᵇᵃ[⊤] E →L[ℝ] F
hl : l.bRiemann = false
B : ι →ᵇᵃ[↑I] ℝ
hB0 : ∀ (J : Box ι), 0 ≤ B J
g : ι →ᵇᵃ[↑I] F
s : Set (ι → ℝ)
hs : s.Countable
hlH : l.bHenstock = true
ε : ℝ
ε0 : 0 < ε
δ₁ : ℝ≥0 → (ι → ℝ) → ℝ → { a // 0 < a }
Hδ₁ :
  ∀ (c : ℝ≥0),
    ∀ x ∈ Box.Icc I ∩ s,
      ∀ (ε : ℝ),
        0 < ε →
          ∀ J ≤ I,
            Box.Icc J ⊆ Metric.closedBall x ↑(δ₁ c x ε) →
              x ∈ Box.Icc J → (l.bDistortion = true → J.distortion ≤ c) → dist ((vol J) (f x)) (g J) ≤ ε
δ₂ : ℝ≥0 → (ι → ℝ) → ℝ → { a // 0 < a }
Hδ₂ :
  ∀ (c : ℝ≥0),
    ∀ x ∈ Box.Icc I \ s,
      ∀ (ε : ℝ),
        0 < ε →
          ∀ J ≤ I,
            Box.Icc J ⊆ Metric.closedBall x ↑(δ₂ c x ε) →
              (l.bHenstock = true → x ∈ Box.Icc J) →
                (l.bDistortion = true → J.distortion ≤ c) → dist ((vol J) (f x)) (g J) ≤ ε * B J
ε0' : 0 < ε / 2
H0 : 0 < 2 ^ Fintype.card ι
εs : (ι → ℝ) → ℝ
hεs0 : ∀ (i : ι → ℝ), 0 < εs i
hεs : ∀ (t : Finset (ι → ℝ)), ↑t ⊆ s → ∑ i ∈ t, 2 ^ Fintype.card ι * εs i ≤ ε / 2
ε' : ℝ
ε'0 : 0 < ε'
hεI : B I * ε' < ε / 2
δ : ℝ≥0 → (ι → ℝ) → ↑(Set.Ioi 0) := fun c x ↦ if x ∈ s then δ₁ c x (εs x) else δ₂ c x ε'
π : TaggedPrepartition I
c : ℝ≥0
hπδ : l.MemBaseSet I c (δ c) π
hπp : π.IsPartition
hsne : s.Nonempty
⊢ dist (∑ x ∈ π.boxes with π.tag x ∈ s, (vol x) (f (π.tag x))) (∑ x ∈ π.boxes with π.tag x ∈ s, g x) ≤ ε / 2

Tactic:
have : ∀ J ∈ {J ∈ π.boxes | π.tag J ∈ s},
        dist (vol J (f <| π.tag J)) (g J) ≤ εs (π.tag J) := fun J hJ ↦ by
      rw [Finset.mem_filter] at hJ; obtain ⟨hJ, hJs⟩ := hJ
      refine Hδ₁ c _ ⟨π.tag_mem_Icc _, hJs⟩ _ (hεs0 _) _ (π.le_of_mem' _ hJ) ?_
        (hπδ.2 hlH J hJ) fun hD => (Finset.le_sup hJ).trans (hπδ.3 hD)
      convert! hπδ.1 J hJ using 3; exact (if_pos hJs).symm

Goal state after:
case refine_1.inr
ι : Type u
E : Type v
F : Type w
inst✝⁴ : NormedAddCommGroup E
inst✝³ : NormedSpace ℝ E
inst✝² : NormedAddCommGroup F
inst✝¹ : NormedSpace ℝ F
I : Box ι
inst✝ : Fintype ι
l : IntegrationParams
f : (ι → ℝ) → E
vol : ι →ᵇᵃ[⊤] E →L[ℝ] F
hl : l.bRiemann = false
B : ι →ᵇᵃ[↑I] ℝ
hB0 : ∀ (J : Box ι), 0 ≤ B J
g : ι →ᵇᵃ[↑I] F
s : Set (ι → ℝ)
hs : s.Countable
hlH : l.bHenstock = true
ε : ℝ
ε0 : 0 < ε
δ₁ : ℝ≥0 → (ι → ℝ) → ℝ → { a // 0 < a }
Hδ₁ :
  ∀ (c : ℝ≥0),
    ∀ x ∈ Box.Icc I ∩ s,
      ∀ (ε : ℝ),
        0 < ε →
          ∀ J ≤ I,
            Box.Icc J ⊆ Metric.closedBall x ↑(δ₁ c x ε) →
              x ∈ Box.Icc J → (l.bDistortion = true → J.distortion ≤ c) → dist ((vol J) (f x)) (g J) ≤ ε
δ₂ : ℝ≥0 → (ι → ℝ) → ℝ → { a // 0 < a }
Hδ₂ :
  ∀ (c : ℝ≥0),
    ∀ x ∈ Box.Icc I \ s,
      ∀ (ε : ℝ),
        0 < ε →
          ∀ J ≤ I,
            Box.Icc J ⊆ Metric.closedBall x ↑(δ₂ c x ε) →
              (l.bHenstock = true → x ∈ Box.Icc J) →
                (l.bDistortion = true → J.distortion ≤ c) → dist ((vol J) (f x)) (g J) ≤ ε * B J
ε0' : 0 < ε / 2
H0 : 0 < 2 ^ Fintype.card ι
εs : (ι → ℝ) → ℝ
hεs0 : ∀ (i : ι → ℝ), 0 < εs i
hεs : ∀ (t : Finset (ι → ℝ)), ↑t ⊆ s → ∑ i ∈ t, 2 ^ Fintype.card ι * εs i ≤ ε / 2
ε' : ℝ
ε'0 : 0 < ε'
hεI : B I * ε' < ε / 2
δ : ℝ≥0 → (ι → ℝ) → ↑(Set.Ioi 0) := fun c x ↦ if x ∈ s then δ₁ c x (εs x) else δ₂ c x ε'
π : TaggedPrepartition I
c : ℝ≥0
hπδ : l.MemBaseSet I c (δ c) π
hπp : π.IsPartition
hsne : s.Nonempty
this : ∀ J ∈ {J ∈ π.boxes | π.tag J ∈ s}, dist ((vol J) (f (π.tag J))) (g J) ≤ εs (π.tag J)
⊢ dist (∑ x ∈ π.boxes with π.tag x ∈ s, (vol x) (f (π.tag x))) (∑ x ∈ π.boxes with π.tag x ∈ s, g x) ≤ ε / 2