-- Mathlib/Analysis/BoxIntegral/Integrability.lean
theorem AEContinuous.hasBoxIntegral [CompleteSpace E] {f : (ι → ℝ) → E} (μ : Measure (ι → ℝ))
    [IsLocallyFiniteMeasure μ] {I : Box ι} (hb : ∃ C : ℝ, ∀ x ∈ Box.Icc I, ‖f x‖ ≤ C)
    (hc : ∀ᵐ x ∂μ, ContinuousAt f x) (l : IntegrationParams) :
    HasIntegral.{u, v, v} I l f μ.toBoxAdditive.toSMul (∫ x in I, f x ∂μ)

Proof state:
case h.e'_13.right
ι : Type u
E : Type v
inst✝⁴ : Fintype ι
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
inst✝¹ : CompleteSpace E
f : (ι → ℝ) → E
μ : Measure (ι → ℝ)
inst✝ : IsLocallyFiniteMeasure μ
I : Box ι
hb : ∃ C, ∀ x ∈ Box.Icc I, ‖f x‖ ≤ C
hc : ∀ᵐ (x : ι → ℝ) ∂μ, ContinuousAt f x
l : IntegrationParams
y : E
hy : HasIntegral I l f μ.toBoxAdditive.toSMul y
this✝ : IsFiniteMeasure (μ.restrict (Box.Icc I))
this : IsFiniteMeasure (μ.restrict ↑I)
⊢ HasFiniteIntegral f (μ.restrict ↑I)

Tactic:
obtain ⟨C, hC⟩ := hb

Result:
case h.e'_13.right.intro
ι : Type u
E : Type v
inst✝⁴ : Fintype ι
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
inst✝¹ : CompleteSpace E
f : (ι → ℝ) → E
μ : Measure (ι → ℝ)
inst✝ : IsLocallyFiniteMeasure μ
I : Box ι
hc : ∀ᵐ (x : ι → ℝ) ∂μ, ContinuousAt f x
l : IntegrationParams
y : E
hy : HasIntegral I l f μ.toBoxAdditive.toSMul y
this✝ : IsFiniteMeasure (μ.restrict (Box.Icc I))
this : IsFiniteMeasure (μ.restrict ↑I)
C : ℝ
hC : ∀ x ∈ Box.Icc I, ‖f x‖ ≤ C
⊢ HasFiniteIntegral f (μ.restrict ↑I)

Proof state:
case intro
ι : Type u
E : Type v
inst✝⁴ : Fintype ι
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
inst✝¹ : CompleteSpace E
f : (ι → ℝ) → E
μ : Measure (ι → ℝ)
inst✝ : IsLocallyFiniteMeasure μ
I : Box ι
hb : ∃ C, ∀ x ∈ Box.Icc I, ‖f x‖ ≤ C
hc : ∀ᵐ (x : ι → ℝ) ∂μ, ContinuousAt f x
l : IntegrationParams
y : E
hy : HasIntegral I l f μ.toBoxAdditive.toSMul y
⊢ HasIntegral I l f μ.toBoxAdditive.toSMul (∫ (x : ι → ℝ) in ↑I, f x ∂μ)

Tactic:
convert hy

Result:
case h.e'_13
ι : Type u
E : Type v
inst✝⁴ : Fintype ι
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
inst✝¹ : CompleteSpace E
f : (ι → ℝ) → E
μ : Measure (ι → ℝ)
inst✝ : IsLocallyFiniteMeasure μ
I : Box ι
hb : ∃ C, ∀ x ∈ Box.Icc I, ‖f x‖ ≤ C
hc : ∀ᵐ (x : ι → ℝ) ∂μ, ContinuousAt f x
l : IntegrationParams
y : E
hy : HasIntegral I l f μ.toBoxAdditive.toSMul y
⊢ ∫ (x : ι → ℝ) in ↑I, f x ∂μ = y

Proof state:
case h.e'_13.left
ι : Type u
E : Type v
inst✝⁴ : Fintype ι
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
inst✝¹ : CompleteSpace E
f : (ι → ℝ) → E
μ : Measure (ι → ℝ)
inst✝ : IsLocallyFiniteMeasure μ
I : Box ι
hb : ∃ C, ∀ x ∈ Box.Icc I, ‖f x‖ ≤ C
hc : ∀ᵐ (x : ι → ℝ) ∂μ, ContinuousAt f x
l : IntegrationParams
y : E
hy : HasIntegral I l f μ.toBoxAdditive.toSMul y
v : Set (ι → ℝ) := {x | ContinuousAt f x}
this : AEStronglyMeasurable f (μ.restrict v)
s : Set (ι → ℝ)
hs : MeasurableSet s
⊢ μ (s ∩ ↑I) ≤ μ (s ∩ v)

Tactic:
apply le_of_le_of_eq <| μ.mono s.inter_subset_left

Result:
case h.e'_13.left
ι : Type u
E : Type v
inst✝⁴ : Fintype ι
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
inst✝¹ : CompleteSpace E
f : (ι → ℝ) → E
μ : Measure (ι → ℝ)
inst✝ : IsLocallyFiniteMeasure μ
I : Box ι
hb : ∃ C, ∀ x ∈ Box.Icc I, ‖f x‖ ≤ C
hc : ∀ᵐ (x : ι → ℝ) ∂μ, ContinuousAt f x
l : IntegrationParams
y : E
hy : HasIntegral I l f μ.toBoxAdditive.toSMul y
v : Set (ι → ℝ) := {x | ContinuousAt f x}
this : AEStronglyMeasurable f (μ.restrict v)
s : Set (ι → ℝ)
hs : MeasurableSet s
⊢ μ.measureOf s = μ (s ∩ v)

Proof state:
case h.e'_13.right.intro
ι : Type u
E : Type v
inst✝⁴ : Fintype ι
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
inst✝¹ : CompleteSpace E
f : (ι → ℝ) → E
μ : Measure (ι → ℝ)
inst✝ : IsLocallyFiniteMeasure μ
I : Box ι
hc : ∀ᵐ (x : ι → ℝ) ∂μ, ContinuousAt f x
l : IntegrationParams
y : E
hy : HasIntegral I l f μ.toBoxAdditive.toSMul y
this✝ : IsFiniteMeasure (μ.restrict (Box.Icc I))
this : IsFiniteMeasure (μ.restrict ↑I)
C : ℝ
hC : ∀ x ∈ Box.Icc I, ‖f x‖ ≤ C
⊢ HasFiniteIntegral f (μ.restrict ↑I)

Tactic:
refine hasFiniteIntegral_of_bounded (C := C) (Filter.eventually_iff_exists_mem.2 ?_)

Result:
case h.e'_13.right.intro
ι : Type u
E : Type v
inst✝⁴ : Fintype ι
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
inst✝¹ : CompleteSpace E
f : (ι → ℝ) → E
μ : Measure (ι → ℝ)
inst✝ : IsLocallyFiniteMeasure μ
I : Box ι
hc : ∀ᵐ (x : ι → ℝ) ∂μ, ContinuousAt f x
l : IntegrationParams
y : E
hy : HasIntegral I l f μ.toBoxAdditive.toSMul y
this✝ : IsFiniteMeasure (μ.restrict (Box.Icc I))
this : IsFiniteMeasure (μ.restrict ↑I)
C : ℝ
hC : ∀ x ∈ Box.Icc I, ‖f x‖ ≤ C
⊢ ∃ v ∈ ae (μ.restrict ↑I), ∀ y ∈ v, ‖f y‖ ≤ C

Proof state:
case h.e'_13.right.intro
ι : Type u
E : Type v
inst✝⁴ : Fintype ι
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
inst✝¹ : CompleteSpace E
f : (ι → ℝ) → E
μ : Measure (ι → ℝ)
inst✝ : IsLocallyFiniteMeasure μ
I : Box ι
hc : ∀ᵐ (x : ι → ℝ) ∂μ, ContinuousAt f x
l : IntegrationParams
y : E
hy : HasIntegral I l f μ.toBoxAdditive.toSMul y
this✝ : IsFiniteMeasure (μ.restrict (Box.Icc I))
this : IsFiniteMeasure (μ.restrict ↑I)
C : ℝ
hC : ∀ x ∈ Box.Icc I, ‖f x‖ ≤ C
⊢ ∃ v ∈ ae (μ.restrict ↑I), ∀ y ∈ v, ‖f y‖ ≤ C

Tactic:
use I, self_mem_ae_restrict I.measurableSet_coe, fun y hy ↦ hC y (I.coe_subset_Icc hy)

Result:
no goals

Proof state:
ι : Type u
E : Type v
inst✝⁴ : Fintype ι
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
inst✝¹ : CompleteSpace E
f : (ι → ℝ) → E
μ : Measure (ι → ℝ)
inst✝ : IsLocallyFiniteMeasure μ
I : Box ι
hb : ∃ C, ∀ x ∈ Box.Icc I, ‖f x‖ ≤ C
hc : ∀ᵐ (x : ι → ℝ) ∂μ, ContinuousAt f x
l : IntegrationParams
y : E
hy : HasIntegral I l f μ.toBoxAdditive.toSMul y
⊢ (μ.restrict (Box.Icc I)) Set.univ < ⊤

Tactic:
simp [I.isCompact_Icc.measure_lt_top (μ := μ)]

Result:
no goals

Proof state:
case h.e'_13.left
ι : Type u
E : Type v
inst✝⁴ : Fintype ι
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
inst✝¹ : CompleteSpace E
f : (ι → ℝ) → E
μ : Measure (ι → ℝ)
inst✝ : IsLocallyFiniteMeasure μ
I : Box ι
hb : ∃ C, ∀ x ∈ Box.Icc I, ‖f x‖ ≤ C
hc : ∀ᵐ (x : ι → ℝ) ∂μ, ContinuousAt f x
l : IntegrationParams
y : E
hy : HasIntegral I l f μ.toBoxAdditive.toSMul y
v : Set (ι → ℝ) := {x | ContinuousAt f x}
this : AEStronglyMeasurable f (μ.restrict v)
s : Set (ι → ℝ)
hs : MeasurableSet s
⊢ μ (s ∩ ↑I) ≤ (μ.restrict v) s

Tactic:
rw [μ.restrict_apply hs]

Result:
case h.e'_13.left
ι : Type u
E : Type v
inst✝⁴ : Fintype ι
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
inst✝¹ : CompleteSpace E
f : (ι → ℝ) → E
μ : Measure (ι → ℝ)
inst✝ : IsLocallyFiniteMeasure μ
I : Box ι
hb : ∃ C, ∀ x ∈ Box.Icc I, ‖f x‖ ≤ C
hc : ∀ᵐ (x : ι → ℝ) ∂μ, ContinuousAt f x
l : IntegrationParams
y : E
hy : HasIntegral I l f μ.toBoxAdditive.toSMul y
v : Set (ι → ℝ) := {x | ContinuousAt f x}
this : AEStronglyMeasurable f (μ.restrict v)
s : Set (ι → ℝ)
hs : MeasurableSet s
⊢ μ (s ∩ ↑I) ≤ μ (s ∩ v)

Proof state:
case h.e'_13.left
ι : Type u
E : Type v
inst✝⁴ : Fintype ι
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
inst✝¹ : CompleteSpace E
f : (ι → ℝ) → E
μ : Measure (ι → ℝ)
inst✝ : IsLocallyFiniteMeasure μ
I : Box ι
hb : ∃ C, ∀ x ∈ Box.Icc I, ‖f x‖ ≤ C
hc : ∀ᵐ (x : ι → ℝ) ∂μ, ContinuousAt f x
l : IntegrationParams
y : E
hy : HasIntegral I l f μ.toBoxAdditive.toSMul y
v : Set (ι → ℝ) := {x | ContinuousAt f x}
this : AEStronglyMeasurable f (μ.restrict v)
s : Set (ι → ℝ)
hs : MeasurableSet s
⊢ (μ.restrict ↑I) s ≤ (μ.restrict v) s

Tactic:
repeat rw [μ.restrict_apply hs]

Result:
case h.e'_13.left
ι : Type u
E : Type v
inst✝⁴ : Fintype ι
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
inst✝¹ : CompleteSpace E
f : (ι → ℝ) → E
μ : Measure (ι → ℝ)
inst✝ : IsLocallyFiniteMeasure μ
I : Box ι
hb : ∃ C, ∀ x ∈ Box.Icc I, ‖f x‖ ≤ C
hc : ∀ᵐ (x : ι → ℝ) ∂μ, ContinuousAt f x
l : IntegrationParams
y : E
hy : HasIntegral I l f μ.toBoxAdditive.toSMul y
v : Set (ι → ℝ) := {x | ContinuousAt f x}
this : AEStronglyMeasurable f (μ.restrict v)
s : Set (ι → ℝ)
hs : MeasurableSet s
⊢ μ (s ∩ ↑I) ≤ μ (s ∩ v)