Theorem: Besicovitch.tendsto_filterAt
File: Mathlib/MeasureTheory/Covering/Besicovitch.lean

Proof steps:
state_before: α : Type u_1
inst✝⁵ : MetricSpace α
β : Type u
inst✝⁴ : SecondCountableTopology α
inst✝³ : MeasurableSpace α
inst✝² : OpensMeasurableSpace α
inst✝¹ : HasBesicovitchCovering α
μ : Measure α
inst✝ : SFinite μ
x : α
⊢ Tendsto (fun r => closedBall x r) (𝓝[>] 0) ((Besicovitch.vitaliFamily μ).filterAt x)
state_after: α : Type u_1
inst✝⁵ : MetricSpace α
β : Type u
inst✝⁴ : SecondCountableTopology α
inst✝³ : MeasurableSpace α
inst✝² : OpensMeasurableSpace α
inst✝¹ : HasBesicovitchCovering α
μ : Measure α
inst✝ : SFinite μ
x : α
s : Set (Set α)
hs : s ∈ (Besicovitch.vitaliFamily μ).filterAt x
⊢ s ∈ map (fun r => closedBall x r) (𝓝[>] 0)
tactic: intro s hs
state_before: α : Type u_1
inst✝⁵ : MetricSpace α
β : Type u
inst✝⁴ : SecondCountableTopology α
inst✝³ : MeasurableSpace α
inst✝² : OpensMeasurableSpace α
inst✝¹ : HasBesicovitchCovering α
μ : Measure α
inst✝ : SFinite μ
x : α
s : Set (Set α)
hs : s ∈ (Besicovitch.vitaliFamily μ).filterAt x
⊢ s ∈ map (fun r => closedBall x r) (𝓝[>] 0)
state_after: α : Type u_1
inst✝⁵ : MetricSpace α
β : Type u
inst✝⁴ : SecondCountableTopology α
inst✝³ : MeasurableSpace α
inst✝² : OpensMeasurableSpace α
inst✝¹ : HasBesicovitchCovering α
μ : Measure α
inst✝ : SFinite μ
x : α
s : Set (Set α)
hs : s ∈ (Besicovitch.vitaliFamily μ).filterAt x
⊢ (fun r => closedBall x r) ⁻¹' s ∈ 𝓝[>] 0
tactic: simp only [mem_map]
state_before: α : Type u_1
inst✝⁵ : MetricSpace α
β : Type u
inst✝⁴ : SecondCountableTopology α
inst✝³ : MeasurableSpace α
inst✝² : OpensMeasurableSpace α
inst✝¹ : HasBesicovitchCovering α
μ : Measure α
inst✝ : SFinite μ
x : α
s : Set (Set α)
hs : s ∈ (Besicovitch.vitaliFamily μ).filterAt x
⊢ (fun r => closedBall x r) ⁻¹' s ∈ 𝓝[>] 0
state_after: case intro.intro
α : Type u_1
inst✝⁵ : MetricSpace α
β : Type u
inst✝⁴ : SecondCountableTopology α
inst✝³ : MeasurableSpace α
inst✝² : OpensMeasurableSpace α
inst✝¹ : HasBesicovitchCovering α
μ : Measure α
inst✝ : SFinite μ
x : α
s : Set (Set α)
hs : s ∈ (Besicovitch.vitaliFamily μ).filterAt x
ε : ℝ
εpos : ε > 0
hε : ∀ a ∈ (Besicovitch.vitaliFamily μ).setsAt x, a ⊆ closedBall x ε → a ∈ s
⊢ (fun r => closedBall x r) ⁻¹' s ∈ 𝓝[>] 0
tactic: obtain ⟨ε, εpos, hε⟩ :
    ∃ (ε : ℝ), ε > 0 ∧
      ∀ a : Set α, a ∈ (Besicovitch.vitaliFamily μ).setsAt x → a ⊆ closedBall x ε → a ∈ s :=
    (VitaliFamily.mem_filterAt_iff _).1 hs
state_before: case intro.intro
α : Type u_1
inst✝⁵ : MetricSpace α
β : Type u
inst✝⁴ : SecondCountableTopology α
inst✝³ : MeasurableSpace α
inst✝² : OpensMeasurableSpace α
inst✝¹ : HasBesicovitchCovering α
μ : Measure α
inst✝ : SFinite μ
x : α
s : Set (Set α)
hs : s ∈ (Besicovitch.vitaliFamily μ).filterAt x
ε : ℝ
εpos : ε > 0
hε : ∀ a ∈ (Besicovitch.vitaliFamily μ).setsAt x, a ⊆ closedBall x ε → a ∈ s
⊢ (fun r => closedBall x r) ⁻¹' s ∈ 𝓝[>] 0
state_after: case intro.intro
α : Type u_1
inst✝⁵ : MetricSpace α
β : Type u
inst✝⁴ : SecondCountableTopology α
inst✝³ : MeasurableSpace α
inst✝² : OpensMeasurableSpace α
inst✝¹ : HasBesicovitchCovering α
μ : Measure α
inst✝ : SFinite μ
x : α
s : Set (Set α)
hs : s ∈ (Besicovitch.vitaliFamily μ).filterAt x
ε : ℝ
εpos : ε > 0
hε : ∀ a ∈ (Besicovitch.vitaliFamily μ).setsAt x, a ⊆ closedBall x ε → a ∈ s
this : Ioc 0 ε ∈ 𝓝[>] 0
⊢ (fun r => closedBall x r) ⁻¹' s ∈ 𝓝[>] 0
tactic: have : Ioc (0 : ℝ) ε ∈ 𝓝[>] (0 : ℝ) := Ioc_mem_nhdsWithin_Ioi ⟨le_rfl, εpos⟩
state_before: case intro.intro
α : Type u_1
inst✝⁵ : MetricSpace α
β : Type u
inst✝⁴ : SecondCountableTopology α
inst✝³ : MeasurableSpace α
inst✝² : OpensMeasurableSpace α
inst✝¹ : HasBesicovitchCovering α
μ : Measure α
inst✝ : SFinite μ
x : α
s : Set (Set α)
hs : s ∈ (Besicovitch.vitaliFamily μ).filterAt x
ε : ℝ
εpos : ε > 0
hε : ∀ a ∈ (Besicovitch.vitaliFamily μ).setsAt x, a ⊆ closedBall x ε → a ∈ s
this : Ioc 0 ε ∈ 𝓝[>] 0
⊢ (fun r => closedBall x r) ⁻¹' s ∈ 𝓝[>] 0
state_after: case h
α : Type u_1
inst✝⁵ : MetricSpace α
β : Type u
inst✝⁴ : SecondCountableTopology α
inst✝³ : MeasurableSpace α
inst✝² : OpensMeasurableSpace α
inst✝¹ : HasBesicovitchCovering α
μ : Measure α
inst✝ : SFinite μ
x : α
s : Set (Set α)
hs : s ∈ (Besicovitch.vitaliFamily μ).filterAt x
ε : ℝ
εpos : ε > 0
hε : ∀ a ∈ (Besicovitch.vitaliFamily μ).setsAt x, a ⊆ closedBall x ε → a ∈ s
this : Ioc 0 ε ∈ 𝓝[>] 0
a✝ : ℝ
hr : a✝ ∈ Ioc 0 ε
⊢ a✝ ∈ (fun r => closedBall x r) ⁻¹' s
tactic: filter_upwards [this] with _ hr
state_before: case h
α : Type u_1
inst✝⁵ : MetricSpace α
β : Type u
inst✝⁴ : SecondCountableTopology α
inst✝³ : MeasurableSpace α
inst✝² : OpensMeasurableSpace α
inst✝¹ : HasBesicovitchCovering α
μ : Measure α
inst✝ : SFinite μ
x : α
s : Set (Set α)
hs : s ∈ (Besicovitch.vitaliFamily μ).filterAt x
ε : ℝ
εpos : ε > 0
hε : ∀ a ∈ (Besicovitch.vitaliFamily μ).setsAt x, a ⊆ closedBall x ε → a ∈ s
this : Ioc 0 ε ∈ 𝓝[>] 0
a✝ : ℝ
hr : a✝ ∈ Ioc 0 ε
⊢ a✝ ∈ (fun r => closedBall x r) ⁻¹' s
state_after: case h.a
α : Type u_1
inst✝⁵ : MetricSpace α
β : Type u
inst✝⁴ : SecondCountableTopology α
inst✝³ : MeasurableSpace α
inst✝² : OpensMeasurableSpace α
inst✝¹ : HasBesicovitchCovering α
μ : Measure α
inst✝ : SFinite μ
x : α
s : Set (Set α)
hs : s ∈ (Besicovitch.vitaliFamily μ).filterAt x
ε : ℝ
εpos : ε > 0
hε : ∀ a ∈ (Besicovitch.vitaliFamily μ).setsAt x, a ⊆ closedBall x ε → a ∈ s
this : Ioc 0 ε ∈ 𝓝[>] 0
a✝ : ℝ
hr : a✝ ∈ Ioc 0 ε
⊢ (fun r => closedBall x r) a✝ ∈ (Besicovitch.vitaliFamily μ).setsAt x

case h.a
α : Type u_1
inst✝⁵ : MetricSpace α
β : Type u
inst✝⁴ : SecondCountableTopology α
inst✝³ : MeasurableSpace α
inst✝² : OpensMeasurableSpace α
inst✝¹ : HasBesicovitchCovering α
μ : Measure α
inst✝ : SFinite μ
x : α
s : Set (Set α)
hs : s ∈ (Besicovitch.vitaliFamily μ).filterAt x
ε : ℝ
εpos : ε > 0
hε : ∀ a ∈ (Besicovitch.vitaliFamily μ).setsAt x, a ⊆ closedBall x ε → a ∈ s
this : Ioc 0 ε ∈ 𝓝[>] 0
a✝ : ℝ
hr : a✝ ∈ Ioc 0 ε
⊢ (fun r => closedBall x r) a✝ ⊆ closedBall x ε
tactic: apply hε