Theorem: MeasureTheory.SimpleFunc.exists_le_lowerSemicontinuous_lintegral_ge
File: Mathlib/MeasureTheory/Integral/VitaliCaratheodory.lean

tactic: induction' f using MeasureTheory.SimpleFunc.induction with c s hs f₁ f₂ _ h₁ h₂ generalizing ε
state_before: α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
f : α →ₛ ℝ≥0
ε : ℝ≥0∞
ε0 : ε ≠ 0
⊢ ∃ g, (∀ (x : α), ↑f x ≤ g x) ∧ LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f x) ∂μ) + ε

tactic: let f := SimpleFunc.piecewise s hs (SimpleFunc.const α c) (SimpleFunc.const α 0)
state_before: case h_ind
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
⊢ ∃ g,
    (∀ (x : α), ↑(piecewise s hs (const α c) (const α 0)) x ≤ g x) ∧
      LowerSemicontinuous g ∧
        (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑(piecewise s hs (const α c) (const α 0)) x) ∂μ) + ε

tactic: by_cases h : (∫⁻ x, f x ∂μ) = ⊤
state_before: case h_ind
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
⊢ ∃ g,
    (∀ (x : α), ↑(piecewise s hs (const α c) (const α 0)) x ≤ g x) ∧
      LowerSemicontinuous g ∧
        (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑(piecewise s hs (const α c) (const α 0)) x) ∂μ) + ε

tactic: by_cases hc : c = 0
state_before: case neg
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
⊢ ∃ g,
    (∀ (x : α), ↑(piecewise s hs (const α c) (const α 0)) x ≤ g x) ∧
      LowerSemicontinuous g ∧
        (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑(piecewise s hs (const α c) (const α 0)) x) ∂μ) + ε

tactic: have : μ s < μ s + ε / c := by
  have : (0 : ℝ≥0∞) < ε / c := ENNReal.div_pos_iff.2 ⟨ε0, ENNReal.coe_ne_top⟩
  simpa using ENNReal.add_lt_add_left ?aux this
state_before: case neg
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : ¬c = 0
⊢ ∃ g,
    (∀ (x : α), ↑(piecewise s hs (const α c) (const α 0)) x ≤ g x) ∧
      LowerSemicontinuous g ∧
        (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑(piecewise s hs (const α c) (const α 0)) x) ∂μ) + ε

tactic: case aux =>
  classical
  simpa [hs, hc, lt_top_iff_ne_top, true_and_iff, SimpleFunc.coe_const,
    Function.const_apply, lintegral_const, ENNReal.coe_indicator, Set.univ_inter,
    ENNReal.coe_ne_top, MeasurableSet.univ, ENNReal.mul_eq_top, SimpleFunc.const_zero,
    or_false_iff, lintegral_indicator, ENNReal.coe_eq_zero, Ne.def, not_false_iff,
    SimpleFunc.coe_zero, Set.piecewise_eq_indicator, SimpleFunc.coe_piecewise, false_and_iff,
    restrict_apply] using h
state_before: case aux
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : ¬c = 0
this : 0 < ε / ↑c
⊢ ↑↑μ s ≠ ⊤

case neg
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : ¬c = 0
this : ↑↑μ s < ↑↑μ s + ε / ↑c
⊢ ∃ g,
    (∀ (x : α), ↑(piecewise s hs (const α c) (const α 0)) x ≤ g x) ∧
      LowerSemicontinuous g ∧
        (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑(piecewise s hs (const α c) (const α 0)) x) ∂μ) + ε

tactic: obtain ⟨u, su, u_open, μu⟩ : ∃ (u : _), u ⊇ s ∧ IsOpen u ∧ μ u < μ s + ε / c :=
  s.exists_isOpen_lt_of_lt _ this
state_before: case neg
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : ¬c = 0
this : ↑↑μ s < ↑↑μ s + ε / ↑c
⊢ ∃ g,
    (∀ (x : α), ↑(piecewise s hs (const α c) (const α 0)) x ≤ g x) ∧
      LowerSemicontinuous g ∧
        (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑(piecewise s hs (const α c) (const α 0)) x) ∂μ) + ε

tactic: refine'
  ⟨Set.indicator u fun _ => c, fun x => _, u_open.lowerSemicontinuous_indicator (zero_le _), _⟩
state_before: case neg.intro.intro.intro
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : ¬c = 0
this : ↑↑μ s < ↑↑μ s + ε / ↑c
u : Set α
su : u ⊇ s
u_open : IsOpen u
μu : ↑↑μ u < ↑↑μ s + ε / ↑c
⊢ ∃ g,
    (∀ (x : α), ↑(piecewise s hs (const α c) (const α 0)) x ≤ g x) ∧
      LowerSemicontinuous g ∧
        (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑(piecewise s hs (const α c) (const α 0)) x) ∂μ) + ε

tactic: refine'
  ⟨fun _ => c, fun x => _, lowerSemicontinuous_const, by
    simp only [_root_.top_add, le_top, h]⟩
state_before: case pos
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : (∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
⊢ ∃ g,
    (∀ (x : α), ↑(piecewise s hs (const α c) (const α 0)) x ≤ g x) ∧
      LowerSemicontinuous g ∧
        (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑(piecewise s hs (const α c) (const α 0)) x) ∂μ) + ε

tactic: simp only [SimpleFunc.coe_const, SimpleFunc.const_zero, SimpleFunc.coe_zero,
  Set.piecewise_eq_indicator, SimpleFunc.coe_piecewise]
state_before: case pos
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : (∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
x : α
⊢ ↑(piecewise s hs (const α c) (const α 0)) x ≤ (fun x => c) x

tactic: exact Set.indicator_le_self _ _ _
state_before: case pos
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : (∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
x : α
⊢ Set.piecewise s (Function.const α c) 0 x ≤ c

tactic: simp only [_root_.top_add, le_top, h]
state_before: α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : (∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
⊢ (∫⁻ (x : α), ↑((fun x => c) x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑(piecewise s hs (const α c) (const α 0)) x) ∂μ) + ε

tactic: refine' ⟨fun _ => 0, _, lowerSemicontinuous_const, _⟩
state_before: case pos
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : c = 0
⊢ ∃ g,
    (∀ (x : α), ↑(piecewise s hs (const α c) (const α 0)) x ≤ g x) ∧
      LowerSemicontinuous g ∧
        (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑(piecewise s hs (const α c) (const α 0)) x) ∂μ) + ε

tactic: classical
simp only [hc, Set.indicator_zero', Pi.zero_apply, SimpleFunc.const_zero, imp_true_iff,
  eq_self_iff_true, SimpleFunc.coe_zero, Set.piecewise_eq_indicator,
  SimpleFunc.coe_piecewise, le_zero_iff]
state_before: case pos.refine'_1
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : c = 0
⊢ ∀ (x : α), ↑(piecewise s hs (const α c) (const α 0)) x ≤ (fun x => 0) x

tactic: simp only [hc, Set.indicator_zero', Pi.zero_apply, SimpleFunc.const_zero, imp_true_iff,
  eq_self_iff_true, SimpleFunc.coe_zero, Set.piecewise_eq_indicator,
  SimpleFunc.coe_piecewise, le_zero_iff]
state_before: case pos.refine'_1
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : c = 0
⊢ ∀ (x : α), ↑(piecewise s hs (const α c) (const α 0)) x ≤ (fun x => 0) x

tactic: simp only [lintegral_const, MulZeroClass.zero_mul, zero_le, ENNReal.coe_zero]
state_before: case pos.refine'_2
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : c = 0
⊢ (∫⁻ (x : α), ↑((fun x => 0) x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑(piecewise s hs (const α c) (const α 0)) x) ∂μ) + ε

tactic: have : (0 : ℝ≥0∞) < ε / c := ENNReal.div_pos_iff.2 ⟨ε0, ENNReal.coe_ne_top⟩
state_before: α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : ¬c = 0
⊢ ↑↑μ s < ↑↑μ s + ε / ↑c

tactic: simpa using ENNReal.add_lt_add_left ?aux this
state_before: α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : ¬c = 0
this : 0 < ε / ↑c
⊢ ↑↑μ s < ↑↑μ s + ε / ↑c

tactic: classical
simpa [hs, hc, lt_top_iff_ne_top, true_and_iff, SimpleFunc.coe_const,
  Function.const_apply, lintegral_const, ENNReal.coe_indicator, Set.univ_inter,
  ENNReal.coe_ne_top, MeasurableSet.univ, ENNReal.mul_eq_top, SimpleFunc.const_zero,
  or_false_iff, lintegral_indicator, ENNReal.coe_eq_zero, Ne.def, not_false_iff,
  SimpleFunc.coe_zero, Set.piecewise_eq_indicator, SimpleFunc.coe_piecewise, false_and_iff,
  restrict_apply] using h
state_before: α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : ¬c = 0
this : 0 < ε / ↑c
⊢ ↑↑μ s ≠ ⊤

tactic: simpa [hs, hc, lt_top_iff_ne_top, true_and_iff, SimpleFunc.coe_const,
  Function.const_apply, lintegral_const, ENNReal.coe_indicator, Set.univ_inter,
  ENNReal.coe_ne_top, MeasurableSet.univ, ENNReal.mul_eq_top, SimpleFunc.const_zero,
  or_false_iff, lintegral_indicator, ENNReal.coe_eq_zero, Ne.def, not_false_iff,
  SimpleFunc.coe_zero, Set.piecewise_eq_indicator, SimpleFunc.coe_piecewise, false_and_iff,
  restrict_apply] using h
state_before: α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : ¬c = 0
this : 0 < ε / ↑c
⊢ ↑↑μ s ≠ ⊤

tactic: simp only [SimpleFunc.coe_const, SimpleFunc.const_zero, SimpleFunc.coe_zero,
  Set.piecewise_eq_indicator, SimpleFunc.coe_piecewise]
state_before: case neg.intro.intro.intro.refine'_1
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : ¬c = 0
this : ↑↑μ s < ↑↑μ s + ε / ↑c
u : Set α
su : u ⊇ s
u_open : IsOpen u
μu : ↑↑μ u < ↑↑μ s + ε / ↑c
x : α
⊢ ↑(piecewise s hs (const α c) (const α 0)) x ≤ Set.indicator u (fun x => c) x

tactic: exact Set.indicator_le_indicator_of_subset su (fun x => zero_le _) _
state_before: case neg.intro.intro.intro.refine'_1
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : ¬c = 0
this : ↑↑μ s < ↑↑μ s + ε / ↑c
u : Set α
su : u ⊇ s
u_open : IsOpen u
μu : ↑↑μ u < ↑↑μ s + ε / ↑c
x : α
⊢ Set.piecewise s (Function.const α c) 0 x ≤ Set.indicator u (fun x => c) x

tactic: suffices (c : ℝ≥0∞) * μ u ≤ c * μ s + ε by
  classical
  simpa only [ENNReal.coe_indicator, u_open.measurableSet, lintegral_indicator,
    lintegral_const, MeasurableSet.univ, Measure.restrict_apply, Set.univ_inter, const_zero,
    coe_piecewise, coe_const, coe_zero, Set.piecewise_eq_indicator, Function.const_apply, hs]
state_before: case neg.intro.intro.intro.refine'_2
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : ¬c = 0
this : ↑↑μ s < ↑↑μ s + ε / ↑c
u : Set α
su : u ⊇ s
u_open : IsOpen u
μu : ↑↑μ u < ↑↑μ s + ε / ↑c
⊢ (∫⁻ (x : α), ↑(Set.indicator u (fun x => c) x) ∂μ) ≤
    (∫⁻ (x : α), ↑(↑(piecewise s hs (const α c) (const α 0)) x) ∂μ) + ε

tactic: calc
  (c : ℝ≥0∞) * μ u ≤ c * (μ s + ε / c) := mul_le_mul_left' μu.le _
  _ = c * μ s + ε := by
    simp_rw [mul_add]
    rw [ENNReal.mul_div_cancel' _ ENNReal.coe_ne_top]
    simpa using hc
state_before: case neg.intro.intro.intro.refine'_2
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : ¬c = 0
this : ↑↑μ s < ↑↑μ s + ε / ↑c
u : Set α
su : u ⊇ s
u_open : IsOpen u
μu : ↑↑μ u < ↑↑μ s + ε / ↑c
⊢ ↑c * ↑↑μ u ≤ ↑c * ↑↑μ s + ε

tactic: classical
simpa only [ENNReal.coe_indicator, u_open.measurableSet, lintegral_indicator,
  lintegral_const, MeasurableSet.univ, Measure.restrict_apply, Set.univ_inter, const_zero,
  coe_piecewise, coe_const, coe_zero, Set.piecewise_eq_indicator, Function.const_apply, hs]
state_before: α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : ¬c = 0
this✝ : ↑↑μ s < ↑↑μ s + ε / ↑c
u : Set α
su : u ⊇ s
u_open : IsOpen u
μu : ↑↑μ u < ↑↑μ s + ε / ↑c
this : ↑c * ↑↑μ u ≤ ↑c * ↑↑μ s + ε
⊢ (∫⁻ (x : α), ↑(Set.indicator u (fun x => c) x) ∂μ) ≤
    (∫⁻ (x : α), ↑(↑(piecewise s hs (const α c) (const α 0)) x) ∂μ) + ε

tactic: simpa only [ENNReal.coe_indicator, u_open.measurableSet, lintegral_indicator,
  lintegral_const, MeasurableSet.univ, Measure.restrict_apply, Set.univ_inter, const_zero,
  coe_piecewise, coe_const, coe_zero, Set.piecewise_eq_indicator, Function.const_apply, hs]
state_before: α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : ¬c = 0
this✝ : ↑↑μ s < ↑↑μ s + ε / ↑c
u : Set α
su : u ⊇ s
u_open : IsOpen u
μu : ↑↑μ u < ↑↑μ s + ε / ↑c
this : ↑c * ↑↑μ u ≤ ↑c * ↑↑μ s + ε
⊢ (∫⁻ (x : α), ↑(Set.indicator u (fun x => c) x) ∂μ) ≤
    (∫⁻ (x : α), ↑(↑(piecewise s hs (const α c) (const α 0)) x) ∂μ) + ε

tactic: simp_rw [mul_add]
state_before: α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : ¬c = 0
this : ↑↑μ s < ↑↑μ s + ε / ↑c
u : Set α
su : u ⊇ s
u_open : IsOpen u
μu : ↑↑μ u < ↑↑μ s + ε / ↑c
⊢ ↑c * (↑↑μ s + ε / ↑c) = ↑c * ↑↑μ s + ε

tactic: rw [ENNReal.mul_div_cancel' _ ENNReal.coe_ne_top]
state_before: α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : ¬c = 0
this : ↑↑μ s < ↑↑μ s + ε / ↑c
u : Set α
su : u ⊇ s
u_open : IsOpen u
μu : ↑↑μ u < ↑↑μ s + ε / ↑c
⊢ ↑c * ↑↑μ s + ↑c * (ε / ↑c) = ↑c * ↑↑μ s + ε

tactic: simpa using hc
state_before: α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
c : ℝ≥0
s : Set α
hs : MeasurableSet s
ε : ℝ≥0∞
ε0 : ε ≠ 0
f : α →ₛ ℝ≥0 := piecewise s hs (const α c) (const α 0)
h : ¬(∫⁻ (x : α), ↑(↑f x) ∂μ) = ⊤
hc : ¬c = 0
this : ↑↑μ s < ↑↑μ s + ε / ↑c
u : Set α
su : u ⊇ s
u_open : IsOpen u
μu : ↑↑μ u < ↑↑μ s + ε / ↑c
⊢ ↑c ≠ 0

tactic: rcases h₁ (ENNReal.half_pos ε0).ne' with ⟨g₁, f₁_le_g₁, g₁cont, g₁int⟩
state_before: case h_add
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
f₁ f₂ : α →ₛ ℝ≥0
a✝ : Disjoint (Function.support ↑f₁) (Function.support ↑f₂)
h₁ :
  ∀ {ε : ℝ≥0∞},
    ε ≠ 0 →
      ∃ g, (∀ (x : α), ↑f₁ x ≤ g x) ∧ LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₁ x) ∂μ) + ε
h₂ :
  ∀ {ε : ℝ≥0∞},
    ε ≠ 0 →
      ∃ g, (∀ (x : α), ↑f₂ x ≤ g x) ∧ LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₂ x) ∂μ) + ε
ε : ℝ≥0∞
ε0 : ε ≠ 0
⊢ ∃ g,
    (∀ (x : α), ↑(f₁ + f₂) x ≤ g x) ∧
      LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑(f₁ + f₂) x) ∂μ) + ε

tactic: rcases h₂ (ENNReal.half_pos ε0).ne' with ⟨g₂, f₂_le_g₂, g₂cont, g₂int⟩
state_before: case h_add.intro.intro.intro
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
f₁ f₂ : α →ₛ ℝ≥0
a✝ : Disjoint (Function.support ↑f₁) (Function.support ↑f₂)
h₁ :
  ∀ {ε : ℝ≥0∞},
    ε ≠ 0 →
      ∃ g, (∀ (x : α), ↑f₁ x ≤ g x) ∧ LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₁ x) ∂μ) + ε
h₂ :
  ∀ {ε : ℝ≥0∞},
    ε ≠ 0 →
      ∃ g, (∀ (x : α), ↑f₂ x ≤ g x) ∧ LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₂ x) ∂μ) + ε
ε : ℝ≥0∞
ε0 : ε ≠ 0
g₁ : α → ℝ≥0
f₁_le_g₁ : ∀ (x : α), ↑f₁ x ≤ g₁ x
g₁cont : LowerSemicontinuous g₁
g₁int : (∫⁻ (x : α), ↑(g₁ x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₁ x) ∂μ) + ε / 2
⊢ ∃ g,
    (∀ (x : α), ↑(f₁ + f₂) x ≤ g x) ∧
      LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑(f₁ + f₂) x) ∂μ) + ε

tactic: refine'
  ⟨fun x => g₁ x + g₂ x, fun x => add_le_add (f₁_le_g₁ x) (f₂_le_g₂ x), g₁cont.add g₂cont, _⟩
state_before: case h_add.intro.intro.intro.intro.intro.intro
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
f₁ f₂ : α →ₛ ℝ≥0
a✝ : Disjoint (Function.support ↑f₁) (Function.support ↑f₂)
h₁ :
  ∀ {ε : ℝ≥0∞},
    ε ≠ 0 →
      ∃ g, (∀ (x : α), ↑f₁ x ≤ g x) ∧ LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₁ x) ∂μ) + ε
h₂ :
  ∀ {ε : ℝ≥0∞},
    ε ≠ 0 →
      ∃ g, (∀ (x : α), ↑f₂ x ≤ g x) ∧ LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₂ x) ∂μ) + ε
ε : ℝ≥0∞
ε0 : ε ≠ 0
g₁ : α → ℝ≥0
f₁_le_g₁ : ∀ (x : α), ↑f₁ x ≤ g₁ x
g₁cont : LowerSemicontinuous g₁
g₁int : (∫⁻ (x : α), ↑(g₁ x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₁ x) ∂μ) + ε / 2
g₂ : α → ℝ≥0
f₂_le_g₂ : ∀ (x : α), ↑f₂ x ≤ g₂ x
g₂cont : LowerSemicontinuous g₂
g₂int : (∫⁻ (x : α), ↑(g₂ x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₂ x) ∂μ) + ε / 2
⊢ ∃ g,
    (∀ (x : α), ↑(f₁ + f₂) x ≤ g x) ∧
      LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑(f₁ + f₂) x) ∂μ) + ε

tactic: simp only [SimpleFunc.coe_add, ENNReal.coe_add, Pi.add_apply]
state_before: case h_add.intro.intro.intro.intro.intro.intro
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
f₁ f₂ : α →ₛ ℝ≥0
a✝ : Disjoint (Function.support ↑f₁) (Function.support ↑f₂)
h₁ :
  ∀ {ε : ℝ≥0∞},
    ε ≠ 0 →
      ∃ g, (∀ (x : α), ↑f₁ x ≤ g x) ∧ LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₁ x) ∂μ) + ε
h₂ :
  ∀ {ε : ℝ≥0∞},
    ε ≠ 0 →
      ∃ g, (∀ (x : α), ↑f₂ x ≤ g x) ∧ LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₂ x) ∂μ) + ε
ε : ℝ≥0∞
ε0 : ε ≠ 0
g₁ : α → ℝ≥0
f₁_le_g₁ : ∀ (x : α), ↑f₁ x ≤ g₁ x
g₁cont : LowerSemicontinuous g₁
g₁int : (∫⁻ (x : α), ↑(g₁ x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₁ x) ∂μ) + ε / 2
g₂ : α → ℝ≥0
f₂_le_g₂ : ∀ (x : α), ↑f₂ x ≤ g₂ x
g₂cont : LowerSemicontinuous g₂
g₂int : (∫⁻ (x : α), ↑(g₂ x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₂ x) ∂μ) + ε / 2
⊢ (∫⁻ (x : α), ↑((fun x => g₁ x + g₂ x) x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑(f₁ + f₂) x) ∂μ) + ε

tactic: rw [lintegral_add_left f₁.measurable.coe_nnreal_ennreal,
  lintegral_add_left g₁cont.measurable.coe_nnreal_ennreal]
state_before: case h_add.intro.intro.intro.intro.intro.intro
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
f₁ f₂ : α →ₛ ℝ≥0
a✝ : Disjoint (Function.support ↑f₁) (Function.support ↑f₂)
h₁ :
  ∀ {ε : ℝ≥0∞},
    ε ≠ 0 →
      ∃ g, (∀ (x : α), ↑f₁ x ≤ g x) ∧ LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₁ x) ∂μ) + ε
h₂ :
  ∀ {ε : ℝ≥0∞},
    ε ≠ 0 →
      ∃ g, (∀ (x : α), ↑f₂ x ≤ g x) ∧ LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₂ x) ∂μ) + ε
ε : ℝ≥0∞
ε0 : ε ≠ 0
g₁ : α → ℝ≥0
f₁_le_g₁ : ∀ (x : α), ↑f₁ x ≤ g₁ x
g₁cont : LowerSemicontinuous g₁
g₁int : (∫⁻ (x : α), ↑(g₁ x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₁ x) ∂μ) + ε / 2
g₂ : α → ℝ≥0
f₂_le_g₂ : ∀ (x : α), ↑f₂ x ≤ g₂ x
g₂cont : LowerSemicontinuous g₂
g₂int : (∫⁻ (x : α), ↑(g₂ x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₂ x) ∂μ) + ε / 2
⊢ (∫⁻ (x : α), ↑(g₁ x) + ↑(g₂ x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₁ x) + ↑(↑f₂ x) ∂μ) + ε

tactic: convert add_le_add g₁int g₂int using 1
state_before: case h_add.intro.intro.intro.intro.intro.intro
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
f₁ f₂ : α →ₛ ℝ≥0
a✝ : Disjoint (Function.support ↑f₁) (Function.support ↑f₂)
h₁ :
  ∀ {ε : ℝ≥0∞},
    ε ≠ 0 →
      ∃ g, (∀ (x : α), ↑f₁ x ≤ g x) ∧ LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₁ x) ∂μ) + ε
h₂ :
  ∀ {ε : ℝ≥0∞},
    ε ≠ 0 →
      ∃ g, (∀ (x : α), ↑f₂ x ≤ g x) ∧ LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₂ x) ∂μ) + ε
ε : ℝ≥0∞
ε0 : ε ≠ 0
g₁ : α → ℝ≥0
f₁_le_g₁ : ∀ (x : α), ↑f₁ x ≤ g₁ x
g₁cont : LowerSemicontinuous g₁
g₁int : (∫⁻ (x : α), ↑(g₁ x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₁ x) ∂μ) + ε / 2
g₂ : α → ℝ≥0
f₂_le_g₂ : ∀ (x : α), ↑f₂ x ≤ g₂ x
g₂cont : LowerSemicontinuous g₂
g₂int : (∫⁻ (x : α), ↑(g₂ x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₂ x) ∂μ) + ε / 2
⊢ ((∫⁻ (a : α), ↑(g₁ a) ∂μ) + ∫⁻ (a : α), ↑(g₂ a) ∂μ) ≤ ((∫⁻ (a : α), ↑(↑f₁ a) ∂μ) + ∫⁻ (a : α), ↑(↑f₂ a) ∂μ) + ε

tactic: simp only
state_before: case h.e'_4
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
f₁ f₂ : α →ₛ ℝ≥0
a✝ : Disjoint (Function.support ↑f₁) (Function.support ↑f₂)
h₁ :
  ∀ {ε : ℝ≥0∞},
    ε ≠ 0 →
      ∃ g, (∀ (x : α), ↑f₁ x ≤ g x) ∧ LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₁ x) ∂μ) + ε
h₂ :
  ∀ {ε : ℝ≥0∞},
    ε ≠ 0 →
      ∃ g, (∀ (x : α), ↑f₂ x ≤ g x) ∧ LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₂ x) ∂μ) + ε
ε : ℝ≥0∞
ε0 : ε ≠ 0
g₁ : α → ℝ≥0
f₁_le_g₁ : ∀ (x : α), ↑f₁ x ≤ g₁ x
g₁cont : LowerSemicontinuous g₁
g₁int : (∫⁻ (x : α), ↑(g₁ x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₁ x) ∂μ) + ε / 2
g₂ : α → ℝ≥0
f₂_le_g₂ : ∀ (x : α), ↑f₂ x ≤ g₂ x
g₂cont : LowerSemicontinuous g₂
g₂int : (∫⁻ (x : α), ↑(g₂ x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₂ x) ∂μ) + ε / 2
⊢ ((∫⁻ (a : α), ↑(↑f₁ a) ∂μ) + ∫⁻ (a : α), ↑(↑f₂ a) ∂μ) + ε =
    (∫⁻ (x : α), ↑(↑f₁ x) ∂μ) + ε / 2 + ((∫⁻ (x : α), ↑(↑f₂ x) ∂μ) + ε / 2)

tactic: conv_lhs => rw [← ENNReal.add_halves ε]
state_before: case h.e'_4
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
f₁ f₂ : α →ₛ ℝ≥0
a✝ : Disjoint (Function.support ↑f₁) (Function.support ↑f₂)
h₁ :
  ∀ {ε : ℝ≥0∞},
    ε ≠ 0 →
      ∃ g, (∀ (x : α), ↑f₁ x ≤ g x) ∧ LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₁ x) ∂μ) + ε
h₂ :
  ∀ {ε : ℝ≥0∞},
    ε ≠ 0 →
      ∃ g, (∀ (x : α), ↑f₂ x ≤ g x) ∧ LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₂ x) ∂μ) + ε
ε : ℝ≥0∞
ε0 : ε ≠ 0
g₁ : α → ℝ≥0
f₁_le_g₁ : ∀ (x : α), ↑f₁ x ≤ g₁ x
g₁cont : LowerSemicontinuous g₁
g₁int : (∫⁻ (x : α), ↑(g₁ x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₁ x) ∂μ) + ε / 2
g₂ : α → ℝ≥0
f₂_le_g₂ : ∀ (x : α), ↑f₂ x ≤ g₂ x
g₂cont : LowerSemicontinuous g₂
g₂int : (∫⁻ (x : α), ↑(g₂ x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₂ x) ∂μ) + ε / 2
⊢ ((∫⁻ (a : α), ↑(↑f₁ a) ∂μ) + ∫⁻ (a : α), ↑(↑f₂ a) ∂μ) + ε =
    (∫⁻ (x : α), ↑(↑f₁ x) ∂μ) + ε / 2 + ((∫⁻ (x : α), ↑(↑f₂ x) ∂μ) + ε / 2)

tactic: abel
state_before: case h.e'_4
α : Type u_1
inst✝³ : TopologicalSpace α
inst✝² : MeasurableSpace α
inst✝¹ : BorelSpace α
μ : Measure α
inst✝ : WeaklyRegular μ
ε✝ : ℝ≥0∞
ε0✝ : ε✝ ≠ 0
f₁ f₂ : α →ₛ ℝ≥0
a✝ : Disjoint (Function.support ↑f₁) (Function.support ↑f₂)
h₁ :
  ∀ {ε : ℝ≥0∞},
    ε ≠ 0 →
      ∃ g, (∀ (x : α), ↑f₁ x ≤ g x) ∧ LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₁ x) ∂μ) + ε
h₂ :
  ∀ {ε : ℝ≥0∞},
    ε ≠ 0 →
      ∃ g, (∀ (x : α), ↑f₂ x ≤ g x) ∧ LowerSemicontinuous g ∧ (∫⁻ (x : α), ↑(g x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₂ x) ∂μ) + ε
ε : ℝ≥0∞
ε0 : ε ≠ 0
g₁ : α → ℝ≥0
f₁_le_g₁ : ∀ (x : α), ↑f₁ x ≤ g₁ x
g₁cont : LowerSemicontinuous g₁
g₁int : (∫⁻ (x : α), ↑(g₁ x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₁ x) ∂μ) + ε / 2
g₂ : α → ℝ≥0
f₂_le_g₂ : ∀ (x : α), ↑f₂ x ≤ g₂ x
g₂cont : LowerSemicontinuous g₂
g₂int : (∫⁻ (x : α), ↑(g₂ x) ∂μ) ≤ (∫⁻ (x : α), ↑(↑f₂ x) ∂μ) + ε / 2
⊢ ((∫⁻ (a : α), ↑(↑f₁ a) ∂μ) + ∫⁻ (a : α), ↑(↑f₂ a) ∂μ) + (ε / 2 + ε / 2) =
    (∫⁻ (x : α), ↑(↑f₁ x) ∂μ) + ε / 2 + ((∫⁻ (x : α), ↑(↑f₂ x) ∂μ) + ε / 2)