-- Mathlib/MeasureTheory/Integral/DominatedConvergence.lean
theorem _root_.Antitone.tendsto_setIntegral (hsm : ∀ i, MeasurableSet (s i)) (h_anti : Antitone s)
    (hfi : IntegrableOn f (s 0) μ) :
    Tendsto (fun i => ∫ a in s i, f a ∂μ) atTop (𝓝 (∫ a in ⋂ n, s n, f a ∂μ))

Proof state:
case refine_2
α : Type u_1
E : Type u_2
inst✝² : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : ℕ → Set α
f : α → E
hsm : ∀ (i : ℕ), MeasurableSet (s i)
h_anti : Antitone s
hfi : IntegrableOn f (s 0) μ
bound : α → ℝ := (s 0).indicator fun a => ‖f a‖
h_int_eq : (fun i => ∫ (a : α) in s i, f a ∂μ) = fun i => ∫ (a : α), (s i).indicator f a ∂μ
⊢ Integrable bound μ

Tactic:
rw [integrable_indicator_iff (hsm 0)]

Result:
case refine_2
α : Type u_1
E : Type u_2
inst✝² : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : ℕ → Set α
f : α → E
hsm : ∀ (i : ℕ), MeasurableSet (s i)
h_anti : Antitone s
hfi : IntegrableOn f (s 0) μ
bound : α → ℝ := (s 0).indicator fun a => ‖f a‖
h_int_eq : (fun i => ∫ (a : α) in s i, f a ∂μ) = fun i => ∫ (a : α), (s i).indicator f a ∂μ
⊢ IntegrableOn (fun a => ‖f a‖) (s 0) μ

Proof state:
α : Type u_1
E : Type u_2
inst✝² : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : ℕ → Set α
f : α → E
hsm : ∀ (i : ℕ), MeasurableSet (s i)
h_anti : Antitone s
hfi : IntegrableOn f (s 0) μ
⊢ Tendsto (fun i => ∫ (a : α) in s i, f a ∂μ) atTop (𝓝 (∫ (a : α) in ⋂ n, s n, f a ∂μ))

Tactic:
let bound : α → ℝ := indicator (s 0) fun a => ‖f a‖

Result:
α : Type u_1
E : Type u_2
inst✝² : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : ℕ → Set α
f : α → E
hsm : ∀ (i : ℕ), MeasurableSet (s i)
h_anti : Antitone s
hfi : IntegrableOn f (s 0) μ
bound : α → ℝ := (s 0).indicator fun a => ‖f a‖
⊢ Tendsto (fun i => ∫ (a : α) in s i, f a ∂μ) atTop (𝓝 (∫ (a : α) in ⋂ n, s n, f a ∂μ))

Proof state:
case refine_4
α : Type u_1
E : Type u_2
inst✝² : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : ℕ → Set α
f : α → E
hsm : ∀ (i : ℕ), MeasurableSet (s i)
h_anti : Antitone s
hfi : IntegrableOn f (s 0) μ
bound : α → ℝ := (s 0).indicator fun a => ‖f a‖
h_int_eq : (fun i => ∫ (a : α) in s i, f a ∂μ) = fun i => ∫ (a : α), (s i).indicator f a ∂μ
⊢ ∀ᵐ (a : α) ∂μ, Tendsto (fun n => (s n).indicator f a) atTop (𝓝 ((⋂ b, s b).indicator f a))

Tactic:
filter_upwards [] with a using le_trans (h_anti.tendsto_indicator _ _ _) (pure_le_nhds _)

Result:
no goals

Proof state:
α : Type u_1
E : Type u_2
inst✝² : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : ℕ → Set α
f : α → E
hsm : ∀ (i : ℕ), MeasurableSet (s i)
h_anti : Antitone s
hfi : IntegrableOn f (s 0) μ
bound : α → ℝ := (s 0).indicator fun a => ‖f a‖
⊢ Tendsto (fun i => ∫ (a : α) in s i, f a ∂μ) atTop (𝓝 (∫ (a : α) in ⋂ n, s n, f a ∂μ))

Tactic:
have h_int_eq : (fun i => ∫ a in s i, f a ∂μ) = fun i => ∫ a, (s i).indicator f a ∂μ :=
  funext fun i => (integral_indicator (hsm i)).symm

Result:
α : Type u_1
E : Type u_2
inst✝² : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : ℕ → Set α
f : α → E
hsm : ∀ (i : ℕ), MeasurableSet (s i)
h_anti : Antitone s
hfi : IntegrableOn f (s 0) μ
bound : α → ℝ := (s 0).indicator fun a => ‖f a‖
h_int_eq : (fun i => ∫ (a : α) in s i, f a ∂μ) = fun i => ∫ (a : α), (s i).indicator f a ∂μ
⊢ Tendsto (fun i => ∫ (a : α) in s i, f a ∂μ) atTop (𝓝 (∫ (a : α) in ⋂ n, s n, f a ∂μ))

Proof state:
case refine_1
α : Type u_1
E : Type u_2
inst✝² : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : ℕ → Set α
f : α → E
hsm : ∀ (i : ℕ), MeasurableSet (s i)
h_anti : Antitone s
hfi : IntegrableOn f (s 0) μ
bound : α → ℝ := (s 0).indicator fun a => ‖f a‖
h_int_eq : (fun i => ∫ (a : α) in s i, f a ∂μ) = fun i => ∫ (a : α), (s i).indicator f a ∂μ
n : ℕ
⊢ AEStronglyMeasurable ((s n).indicator f) μ

Tactic:
rw [aestronglyMeasurable_indicator_iff (hsm n)]

Result:
case refine_1
α : Type u_1
E : Type u_2
inst✝² : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : ℕ → Set α
f : α → E
hsm : ∀ (i : ℕ), MeasurableSet (s i)
h_anti : Antitone s
hfi : IntegrableOn f (s 0) μ
bound : α → ℝ := (s 0).indicator fun a => ‖f a‖
h_int_eq : (fun i => ∫ (a : α) in s i, f a ∂μ) = fun i => ∫ (a : α), (s i).indicator f a ∂μ
n : ℕ
⊢ AEStronglyMeasurable f (μ.restrict (s n))

Proof state:
α : Type u_1
E : Type u_2
inst✝² : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : ℕ → Set α
f : α → E
hsm : ∀ (i : ℕ), MeasurableSet (s i)
h_anti : Antitone s
hfi : IntegrableOn f (s 0) μ
bound : α → ℝ := (s 0).indicator fun a => ‖f a‖
h_int_eq : (fun i => ∫ (a : α) in s i, f a ∂μ) = fun i => ∫ (a : α), (s i).indicator f a ∂μ
⊢ Tendsto (fun i => ∫ (a : α) in s i, f a ∂μ) atTop (𝓝 (∫ (a : α) in ⋂ n, s n, f a ∂μ))

Tactic:
rw [h_int_eq]

Result:
α : Type u_1
E : Type u_2
inst✝² : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : ℕ → Set α
f : α → E
hsm : ∀ (i : ℕ), MeasurableSet (s i)
h_anti : Antitone s
hfi : IntegrableOn f (s 0) μ
bound : α → ℝ := (s 0).indicator fun a => ‖f a‖
h_int_eq : (fun i => ∫ (a : α) in s i, f a ∂μ) = fun i => ∫ (a : α), (s i).indicator f a ∂μ
⊢ Tendsto (fun i => ∫ (a : α), (s i).indicator f a ∂μ) atTop (𝓝 (∫ (a : α) in ⋂ n, s n, f a ∂μ))

Proof state:
case refine_3
α : Type u_1
E : Type u_2
inst✝² : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : ℕ → Set α
f : α → E
hsm : ∀ (i : ℕ), MeasurableSet (s i)
h_anti : Antitone s
hfi : IntegrableOn f (s 0) μ
bound : α → ℝ := (s 0).indicator fun a => ‖f a‖
h_int_eq : (fun i => ∫ (a : α) in s i, f a ∂μ) = fun i => ∫ (a : α), (s i).indicator f a ∂μ
⊢ ∀ (n : ℕ), ∀ᵐ (a : α) ∂μ, (s n).indicator (fun a => ‖f a‖) a ≤ bound a

Tactic:
refine fun n => Eventually.of_forall fun x => ?_

Result:
case refine_3
α : Type u_1
E : Type u_2
inst✝² : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : ℕ → Set α
f : α → E
hsm : ∀ (i : ℕ), MeasurableSet (s i)
h_anti : Antitone s
hfi : IntegrableOn f (s 0) μ
bound : α → ℝ := (s 0).indicator fun a => ‖f a‖
h_int_eq : (fun i => ∫ (a : α) in s i, f a ∂μ) = fun i => ∫ (a : α), (s i).indicator f a ∂μ
n : ℕ
x : α
⊢ (s n).indicator (fun a => ‖f a‖) x ≤ bound x

Proof state:
case refine_2
α : Type u_1
E : Type u_2
inst✝² : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : ℕ → Set α
f : α → E
hsm : ∀ (i : ℕ), MeasurableSet (s i)
h_anti : Antitone s
hfi : IntegrableOn f (s 0) μ
bound : α → ℝ := (s 0).indicator fun a => ‖f a‖
h_int_eq : (fun i => ∫ (a : α) in s i, f a ∂μ) = fun i => ∫ (a : α), (s i).indicator f a ∂μ
⊢ IntegrableOn (fun a => ‖f a‖) (s 0) μ

Tactic:
exact hfi.norm

Result:
no goals

Proof state:
case refine_1
α : Type u_1
E : Type u_2
inst✝² : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : ℕ → Set α
f : α → E
hsm : ∀ (i : ℕ), MeasurableSet (s i)
h_anti : Antitone s
hfi : IntegrableOn f (s 0) μ
bound : α → ℝ := (s 0).indicator fun a => ‖f a‖
h_int_eq : (fun i => ∫ (a : α) in s i, f a ∂μ) = fun i => ∫ (a : α), (s i).indicator f a ∂μ
⊢ ∀ (n : ℕ), AEStronglyMeasurable ((s n).indicator f) μ

Tactic:
intro n

Result:
case refine_1
α : Type u_1
E : Type u_2
inst✝² : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : ℕ → Set α
f : α → E
hsm : ∀ (i : ℕ), MeasurableSet (s i)
h_anti : Antitone s
hfi : IntegrableOn f (s 0) μ
bound : α → ℝ := (s 0).indicator fun a => ‖f a‖
h_int_eq : (fun i => ∫ (a : α) in s i, f a ∂μ) = fun i => ∫ (a : α), (s i).indicator f a ∂μ
n : ℕ
⊢ AEStronglyMeasurable ((s n).indicator f) μ