Module: Mathlib.Analysis.Distribution.AEEqOfIntegralContDiff

Goal state before:
pp: E : Type u_1
inst✝¹³ : NormedAddCommGroup E
inst✝¹² : NormedSpace ℝ E
inst✝¹¹ : FiniteDimensional ℝ E
F : Type u_2
inst✝¹⁰ : NormedAddCommGroup F
inst✝⁹ : NormedSpace ℝ F
inst✝⁸ : CompleteSpace F
H : Type u_3
inst✝⁷ : TopologicalSpace H
I : ModelWithCorners ℝ E H
M : Type u_4
inst✝⁶ : TopologicalSpace M
inst✝⁵ : ChartedSpace H M
inst✝⁴ : IsManifold I ∞ M
inst✝³ : MeasurableSpace M
inst✝² : BorelSpace M
inst✝¹ : T2Space M
f : M → F
μ : Measure M
inst✝ : SigmaCompactSpace M
hf : LocallyIntegrable f μ
h : ∀ (g : M → ℝ), ContMDiff I 𝓘(ℝ, ℝ) ∞ g → HasCompactSupport g → ∫ (x : M), g x • f x ∂μ = 0
this✝² : LocallyCompactSpace H
this✝¹ : LocallyCompactSpace M
this✝ : SecondCountableTopology H
this : SecondCountableTopology M
x✝ : MetricSpace M := metrizableSpaceMetric M
s : Set M
hs : IsCompact s
δ : ℝ
δpos : 0 < δ
hδ : IsCompact (cthickening δ s)
u : ℕ → ℝ
u_pos : ∀ (n : ℕ), u n ∈ Ioo 0 δ
u_lim : Tendsto u atTop (𝓝 0)
v : ℕ → Set M := fun n ↦ thickening (u n) s
K : Set M
K_compact : IsCompact K
vK : ∀ (n : ℕ), v n ⊆ K
g : ℕ → M → ℝ
g_supp : ∀ (n : ℕ), support (g n) = v n
g_diff : ∀ (n : ℕ), ContMDiff I 𝓘(ℝ, ℝ) ∞ (g n)
g_range : ∀ (n : ℕ), range (g n) ⊆ Icc 0 1
hg : ∀ (n : ℕ), ∀ x ∈ s, g n x = 1
bound : M → ℝ := K.indicator fun x ↦ ‖f x‖
A : ∀ (n : ℕ), AEStronglyMeasurable (fun x ↦ g n x • f x) μ
B : Integrable bound μ
C : ∀ (n : ℕ), ∀ᵐ (x : M) ∂μ, ‖g n x • f x‖ ≤ bound x
⊢ Tendsto (fun n ↦ ∫ (x : M), g n x • f x ∂μ) atTop (𝓝 (∫ (x : M), s.indicator f x ∂μ))

Tactic:
have D : ∀ᵐ x ∂μ, Tendsto (fun n => g n x • f x) atTop (𝓝 (s.indicator f x)) := by
      filter_upwards with x
      by_cases hxs : x ∈ s
      · have : ∀ n, g n x = 1 := fun n ↦ hg n x hxs
        simp [this, indicator_of_mem hxs f]
      · simp_rw [indicator_of_notMem hxs f]
        apply tendsto_const_nhds.congr'
        suffices H : ∀ᶠ n in atTop, g n x = 0 by
          filter_upwards [H] with n hn using by simp [hn]
        obtain ⟨ε, εpos, hε⟩ : ∃ ε, 0 < ε ∧ x ∉ thickening ε s := by
          rw [← hs.isClosed.closure_eq, closure_eq_iInter_thickening s] at hxs
          simpa using hxs
        filter_upwards [(tendsto_order.1 u_lim).2 _ εpos] with n hn
        rw [← notMem_support, g_supp]
        contrapose hε
        exact thickening_mono hn.le s hε

Goal state after:
E : Type u_1
inst✝¹³ : NormedAddCommGroup E
inst✝¹² : NormedSpace ℝ E
inst✝¹¹ : FiniteDimensional ℝ E
F : Type u_2
inst✝¹⁰ : NormedAddCommGroup F
inst✝⁹ : NormedSpace ℝ F
inst✝⁸ : CompleteSpace F
H : Type u_3
inst✝⁷ : TopologicalSpace H
I : ModelWithCorners ℝ E H
M : Type u_4
inst✝⁶ : TopologicalSpace M
inst✝⁵ : ChartedSpace H M
inst✝⁴ : IsManifold I ∞ M
inst✝³ : MeasurableSpace M
inst✝² : BorelSpace M
inst✝¹ : T2Space M
f : M → F
μ : Measure M
inst✝ : SigmaCompactSpace M
hf : LocallyIntegrable f μ
h : ∀ (g : M → ℝ), ContMDiff I 𝓘(ℝ, ℝ) ∞ g → HasCompactSupport g → ∫ (x : M), g x • f x ∂μ = 0
this✝² : LocallyCompactSpace H
this✝¹ : LocallyCompactSpace M
this✝ : SecondCountableTopology H
this : SecondCountableTopology M
x✝ : MetricSpace M := metrizableSpaceMetric M
s : Set M
hs : IsCompact s
δ : ℝ
δpos : 0 < δ
hδ : IsCompact (cthickening δ s)
u : ℕ → ℝ
u_pos : ∀ (n : ℕ), u n ∈ Ioo 0 δ
u_lim : Tendsto u atTop (𝓝 0)
v : ℕ → Set M := fun n ↦ thickening (u n) s
K : Set M
K_compact : IsCompact K
vK : ∀ (n : ℕ), v n ⊆ K
g : ℕ → M → ℝ
g_supp : ∀ (n : ℕ), support (g n) = v n
g_diff : ∀ (n : ℕ), ContMDiff I 𝓘(ℝ, ℝ) ∞ (g n)
g_range : ∀ (n : ℕ), range (g n) ⊆ Icc 0 1
hg : ∀ (n : ℕ), ∀ x ∈ s, g n x = 1
bound : M → ℝ := K.indicator fun x ↦ ‖f x‖
A : ∀ (n : ℕ), AEStronglyMeasurable (fun x ↦ g n x • f x) μ
B : Integrable bound μ
C : ∀ (n : ℕ), ∀ᵐ (x : M) ∂μ, ‖g n x • f x‖ ≤ bound x
D : ∀ᵐ (x : M) ∂μ, Tendsto (fun n ↦ g n x • f x) atTop (𝓝 (s.indicator f x))
⊢ Tendsto (fun n ↦ ∫ (x : M), g n x • f x ∂μ) atTop (𝓝 (∫ (x : M), s.indicator f x ∂μ))