-- Mathlib/MeasureTheory/Function/UniformIntegrable.lean
theorem add (hf : UnifIntegrable f p μ) (hg : UnifIntegrable g p μ) (hp : 1 ≤ p)
    (hf_meas : ∀ i, AEStronglyMeasurable (f i) μ) (hg_meas : ∀ i, AEStronglyMeasurable (g i) μ) :
    UnifIntegrable (f + g) p μ

Proof state:
case intro.intro.intro.intro
α : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace α
μ : Measure α
inst✝ : NormedAddCommGroup β
f g : ι → α → β
p : ℝ≥0∞
hf : UnifIntegrable f p μ
hg : UnifIntegrable g p μ
hp : 1 ≤ p
hf_meas : ∀ (i : ι), AEStronglyMeasurable (f i) μ
hg_meas : ∀ (i : ι), AEStronglyMeasurable (g i) μ
ε : ℝ
hε : 0 < ε
hε2 : 0 < ε / 2
δ₁ : ℝ
hδ₁_pos : 0 < δ₁
hfδ₁ :
  ∀ (i : ι) (s : Set α),
    MeasurableSet s → μ s ≤ ENNReal.ofReal δ₁ → eLpNorm (s.indicator (f i)) p μ ≤ ENNReal.ofReal (ε / 2)
δ₂ : ℝ
hδ₂_pos : 0 < δ₂
hgδ₂ :
  ∀ (i : ι) (s : Set α),
    MeasurableSet s → μ s ≤ ENNReal.ofReal δ₂ → eLpNorm (s.indicator (g i)) p μ ≤ ENNReal.ofReal (ε / 2)
i : ι
s : Set α
hs : MeasurableSet s
hμs : μ s ≤ ENNReal.ofReal (δ₁ ⊓ δ₂)
⊢ eLpNorm (s.indicator ((f + g) i)) p μ ≤ ENNReal.ofReal ε

Tactic:
simp_rw [Pi.add_apply, Set.indicator_add']

Result:
case intro.intro.intro.intro
α : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace α
μ : Measure α
inst✝ : NormedAddCommGroup β
f g : ι → α → β
p : ℝ≥0∞
hf : UnifIntegrable f p μ
hg : UnifIntegrable g p μ
hp : 1 ≤ p
hf_meas : ∀ (i : ι), AEStronglyMeasurable (f i) μ
hg_meas : ∀ (i : ι), AEStronglyMeasurable (g i) μ
ε : ℝ
hε : 0 < ε
hε2 : 0 < ε / 2
δ₁ : ℝ
hδ₁_pos : 0 < δ₁
hfδ₁ :
  ∀ (i : ι) (s : Set α),
    MeasurableSet s → μ s ≤ ENNReal.ofReal δ₁ → eLpNorm (s.indicator (f i)) p μ ≤ ENNReal.ofReal (ε / 2)
δ₂ : ℝ
hδ₂_pos : 0 < δ₂
hgδ₂ :
  ∀ (i : ι) (s : Set α),
    MeasurableSet s → μ s ≤ ENNReal.ofReal δ₂ → eLpNorm (s.indicator (g i)) p μ ≤ ENNReal.ofReal (ε / 2)
i : ι
s : Set α
hs : MeasurableSet s
hμs : μ s ≤ ENNReal.ofReal (δ₁ ⊓ δ₂)
⊢ eLpNorm (s.indicator (f i) + s.indicator (g i)) p μ ≤ ENNReal.ofReal ε

Proof state:
α : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace α
μ : Measure α
inst✝ : NormedAddCommGroup β
f g : ι → α → β
p : ℝ≥0∞
hf : UnifIntegrable f p μ
hg : UnifIntegrable g p μ
hp : 1 ≤ p
hf_meas : ∀ (i : ι), AEStronglyMeasurable (f i) μ
hg_meas : ∀ (i : ι), AEStronglyMeasurable (g i) μ
ε : ℝ
hε : 0 < ε
hε2 : 0 < ε / 2
δ₁ : ℝ
hδ₁_pos : 0 < δ₁
hfδ₁ :
  ∀ (i : ι) (s : Set α),
    MeasurableSet s → μ s ≤ ENNReal.ofReal δ₁ → eLpNorm (s.indicator (f i)) p μ ≤ ENNReal.ofReal (ε / 2)
δ₂ : ℝ
hδ₂_pos : 0 < δ₂
hgδ₂ :
  ∀ (i : ι) (s : Set α),
    MeasurableSet s → μ s ≤ ENNReal.ofReal δ₂ → eLpNorm (s.indicator (g i)) p μ ≤ ENNReal.ofReal (ε / 2)
i : ι
s : Set α
hs : MeasurableSet s
hμs : μ s ≤ ENNReal.ofReal (δ₁ ⊓ δ₂)
⊢ ENNReal.ofReal ε = ENNReal.ofReal (ε / 2) + ENNReal.ofReal (ε / 2)

Tactic:
rw [← ENNReal.ofReal_add hε2.le hε2.le, add_halves]

Result:
no goals

Proof state:
case intro.intro.intro.intro
α : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace α
μ : Measure α
inst✝ : NormedAddCommGroup β
f g : ι → α → β
p : ℝ≥0∞
hf : UnifIntegrable f p μ
hg : UnifIntegrable g p μ
hp : 1 ≤ p
hf_meas : ∀ (i : ι), AEStronglyMeasurable (f i) μ
hg_meas : ∀ (i : ι), AEStronglyMeasurable (g i) μ
ε : ℝ
hε : 0 < ε
hε2 : 0 < ε / 2
δ₁ : ℝ
hδ₁_pos : 0 < δ₁
hfδ₁ :
  ∀ (i : ι) (s : Set α),
    MeasurableSet s → μ s ≤ ENNReal.ofReal δ₁ → eLpNorm (s.indicator (f i)) p μ ≤ ENNReal.ofReal (ε / 2)
δ₂ : ℝ
hδ₂_pos : 0 < δ₂
hgδ₂ :
  ∀ (i : ι) (s : Set α),
    MeasurableSet s → μ s ≤ ENNReal.ofReal δ₂ → eLpNorm (s.indicator (g i)) p μ ≤ ENNReal.ofReal (ε / 2)
⊢ ∃ δ,
    ∃ (_ : 0 < δ),
      ∀ (i : ι) (s : Set α),
        MeasurableSet s → μ s ≤ ENNReal.ofReal δ → eLpNorm (s.indicator ((f + g) i)) p μ ≤ ENNReal.ofReal ε

Tactic:
refine ⟨min δ₁ δ₂, lt_min hδ₁_pos hδ₂_pos, fun i s hs hμs => ?_⟩

Result:
case intro.intro.intro.intro
α : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace α
μ : Measure α
inst✝ : NormedAddCommGroup β
f g : ι → α → β
p : ℝ≥0∞
hf : UnifIntegrable f p μ
hg : UnifIntegrable g p μ
hp : 1 ≤ p
hf_meas : ∀ (i : ι), AEStronglyMeasurable (f i) μ
hg_meas : ∀ (i : ι), AEStronglyMeasurable (g i) μ
ε : ℝ
hε : 0 < ε
hε2 : 0 < ε / 2
δ₁ : ℝ
hδ₁_pos : 0 < δ₁
hfδ₁ :
  ∀ (i : ι) (s : Set α),
    MeasurableSet s → μ s ≤ ENNReal.ofReal δ₁ → eLpNorm (s.indicator (f i)) p μ ≤ ENNReal.ofReal (ε / 2)
δ₂ : ℝ
hδ₂_pos : 0 < δ₂
hgδ₂ :
  ∀ (i : ι) (s : Set α),
    MeasurableSet s → μ s ≤ ENNReal.ofReal δ₂ → eLpNorm (s.indicator (g i)) p μ ≤ ENNReal.ofReal (ε / 2)
i : ι
s : Set α
hs : MeasurableSet s
hμs : μ s ≤ ENNReal.ofReal (δ₁ ⊓ δ₂)
⊢ eLpNorm (s.indicator ((f + g) i)) p μ ≤ ENNReal.ofReal ε

Proof state:
α : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace α
μ : Measure α
inst✝ : NormedAddCommGroup β
f g : ι → α → β
p : ℝ≥0∞
hf : UnifIntegrable f p μ
hg : UnifIntegrable g p μ
hp : 1 ≤ p
hf_meas : ∀ (i : ι), AEStronglyMeasurable (f i) μ
hg_meas : ∀ (i : ι), AEStronglyMeasurable (g i) μ
ε : ℝ
hε : 0 < ε
⊢ ∃ δ,
    ∃ (_ : 0 < δ),
      ∀ (i : ι) (s : Set α),
        MeasurableSet s → μ s ≤ ENNReal.ofReal δ → eLpNorm (s.indicator ((f + g) i)) p μ ≤ ENNReal.ofReal ε

Tactic:
have hε2 : 0 < ε / 2 := half_pos hε

Result:
α : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace α
μ : Measure α
inst✝ : NormedAddCommGroup β
f g : ι → α → β
p : ℝ≥0∞
hf : UnifIntegrable f p μ
hg : UnifIntegrable g p μ
hp : 1 ≤ p
hf_meas : ∀ (i : ι), AEStronglyMeasurable (f i) μ
hg_meas : ∀ (i : ι), AEStronglyMeasurable (g i) μ
ε : ℝ
hε : 0 < ε
hε2 : 0 < ε / 2
⊢ ∃ δ,
    ∃ (_ : 0 < δ),
      ∀ (i : ι) (s : Set α),
        MeasurableSet s → μ s ≤ ENNReal.ofReal δ → eLpNorm (s.indicator ((f + g) i)) p μ ≤ ENNReal.ofReal ε

Proof state:
α : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace α
μ : Measure α
inst✝ : NormedAddCommGroup β
f g : ι → α → β
p : ℝ≥0∞
hf : UnifIntegrable f p μ
hg : UnifIntegrable g p μ
hp : 1 ≤ p
hf_meas : ∀ (i : ι), AEStronglyMeasurable (f i) μ
hg_meas : ∀ (i : ι), AEStronglyMeasurable (g i) μ
⊢ UnifIntegrable (f + g) p μ

Tactic:
intro ε hε

Result:
α : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace α
μ : Measure α
inst✝ : NormedAddCommGroup β
f g : ι → α → β
p : ℝ≥0∞
hf : UnifIntegrable f p μ
hg : UnifIntegrable g p μ
hp : 1 ≤ p
hf_meas : ∀ (i : ι), AEStronglyMeasurable (f i) μ
hg_meas : ∀ (i : ι), AEStronglyMeasurable (g i) μ
ε : ℝ
hε : 0 < ε
⊢ ∃ δ,
    ∃ (_ : 0 < δ),
      ∀ (i : ι) (s : Set α),
        MeasurableSet s → μ s ≤ ENNReal.ofReal δ → eLpNorm (s.indicator ((f + g) i)) p μ ≤ ENNReal.ofReal ε

Proof state:
α : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace α
μ : Measure α
inst✝ : NormedAddCommGroup β
f g : ι → α → β
p : ℝ≥0∞
hf : UnifIntegrable f p μ
hg : UnifIntegrable g p μ
hp : 1 ≤ p
hf_meas : ∀ (i : ι), AEStronglyMeasurable (f i) μ
hg_meas : ∀ (i : ι), AEStronglyMeasurable (g i) μ
ε : ℝ
hε : 0 < ε
hε2 : 0 < ε / 2
⊢ ∃ δ,
    ∃ (_ : 0 < δ),
      ∀ (i : ι) (s : Set α),
        MeasurableSet s → μ s ≤ ENNReal.ofReal δ → eLpNorm (s.indicator ((f + g) i)) p μ ≤ ENNReal.ofReal ε

Tactic:
obtain ⟨δ₁, hδ₁_pos, hfδ₁⟩ := hf hε2

Result:
case intro.intro
α : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace α
μ : Measure α
inst✝ : NormedAddCommGroup β
f g : ι → α → β
p : ℝ≥0∞
hf : UnifIntegrable f p μ
hg : UnifIntegrable g p μ
hp : 1 ≤ p
hf_meas : ∀ (i : ι), AEStronglyMeasurable (f i) μ
hg_meas : ∀ (i : ι), AEStronglyMeasurable (g i) μ
ε : ℝ
hε : 0 < ε
hε2 : 0 < ε / 2
δ₁ : ℝ
hδ₁_pos : 0 < δ₁
hfδ₁ :
  ∀ (i : ι) (s : Set α),
    MeasurableSet s → μ s ≤ ENNReal.ofReal δ₁ → eLpNorm (s.indicator (f i)) p μ ≤ ENNReal.ofReal (ε / 2)
⊢ ∃ δ,
    ∃ (_ : 0 < δ),
      ∀ (i : ι) (s : Set α),
        MeasurableSet s → μ s ≤ ENNReal.ofReal δ → eLpNorm (s.indicator ((f + g) i)) p μ ≤ ENNReal.ofReal ε