-- Mathlib/MeasureTheory/Measure/Lebesgue/EqHaar.lean
theorem tendsto_addHaar_inter_smul_one_of_density_one_aux (s : Set E) (hs : MeasurableSet s)
    (x : E) (h : Tendsto (fun r => μ (s ∩ closedBall x r) / μ (closedBall x r)) (𝓝[>] 0) (𝓝 1))
    (t : Set E) (ht : MeasurableSet t) (h't : μ t ≠ 0) (h''t : μ t ≠ ∞) :
    Tendsto (fun r : ℝ => μ (s ∩ ({x} + r • t)) / μ ({x} + r • t)) (𝓝[>] 0) (𝓝 1)

Proof state:
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
inst✝¹ : FiniteDimensional ℝ E
μ : Measure E
inst✝ : μ.IsAddHaarMeasure
s : Set E
hs : MeasurableSet s
x : E
h : Tendsto (fun r => μ (s ∩ closedBall x r) / μ (closedBall x r)) (𝓝[>] 0) (𝓝 1)
t : Set E
ht : MeasurableSet t
h't : μ t ≠ 0
h''t : μ t ≠ ⊤
I : ∀ (u v : Set E), μ u ≠ 0 → μ u ≠ ⊤ → MeasurableSet v → μ u / μ u - μ (vᶜ ∩ u) / μ u = μ (v ∩ u) / μ u
A : Tendsto (fun r => μ (closedBall x r) / μ (closedBall x r)) (𝓝[>] 0) (𝓝 1)
B :
  Tendsto (fun a => μ (closedBall x a) / μ (closedBall x a) - μ (s ∩ closedBall x a) / μ (closedBall x a)) (𝓝[>] 0)
    (𝓝 0)
⊢ (fun a => μ (closedBall x a) / μ (closedBall x a) - μ (s ∩ closedBall x a) / μ (closedBall x a)) =ᶠ[𝓝[>] 0] fun r =>
    μ (sᶜ ∩ closedBall x r) / μ (closedBall x r)

Tactic:
filter_upwards [self_mem_nhdsWithin]

Result:
case h
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
inst✝¹ : FiniteDimensional ℝ E
μ : Measure E
inst✝ : μ.IsAddHaarMeasure
s : Set E
hs : MeasurableSet s
x : E
h : Tendsto (fun r => μ (s ∩ closedBall x r) / μ (closedBall x r)) (𝓝[>] 0) (𝓝 1)
t : Set E
ht : MeasurableSet t
h't : μ t ≠ 0
h''t : μ t ≠ ⊤
I : ∀ (u v : Set E), μ u ≠ 0 → μ u ≠ ⊤ → MeasurableSet v → μ u / μ u - μ (vᶜ ∩ u) / μ u = μ (v ∩ u) / μ u
A : Tendsto (fun r => μ (closedBall x r) / μ (closedBall x r)) (𝓝[>] 0) (𝓝 1)
B :
  Tendsto (fun a => μ (closedBall x a) / μ (closedBall x a) - μ (s ∩ closedBall x a) / μ (closedBall x a)) (𝓝[>] 0)
    (𝓝 0)
⊢ ∀ a ∈ Ioi 0,
    μ (closedBall x a) / μ (closedBall x a) - μ (s ∩ closedBall x a) / μ (closedBall x a) =
      μ (sᶜ ∩ closedBall x a) / μ (closedBall x a)

Proof state:
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
inst✝¹ : FiniteDimensional ℝ E
μ : Measure E
inst✝ : μ.IsAddHaarMeasure
s : Set E
hs : MeasurableSet s
x : E
h : Tendsto (fun r => μ (s ∩ closedBall x r) / μ (closedBall x r)) (𝓝[>] 0) (𝓝 1)
t : Set E
ht : MeasurableSet t
h't : μ t ≠ 0
h''t : μ t ≠ ⊤
I : ∀ (u v : Set E), μ u ≠ 0 → μ u ≠ ⊤ → MeasurableSet v → μ u / μ u - μ (vᶜ ∩ u) / μ u = μ (v ∩ u) / μ u
L : Tendsto (fun r => μ (sᶜ ∩ closedBall x r) / μ (closedBall x r)) (𝓝[>] 0) (𝓝 0)
L' : Tendsto (fun r => μ (sᶜ ∩ ({x} + r • t)) / μ ({x} + r • t)) (𝓝[>] 0) (𝓝 0)
L'' : Tendsto (fun r => μ ({x} + r • t) / μ ({x} + r • t)) (𝓝[>] 0) (𝓝 1)
this : Tendsto (fun a => μ ({x} + a • t) / μ ({x} + a • t) - μ (sᶜ ∩ ({x} + a • t)) / μ ({x} + a • t)) (𝓝[>] 0) (𝓝 1)
⊢ (fun a => μ ({x} + a • t) / μ ({x} + a • t) - μ (sᶜ ∩ ({x} + a • t)) / μ ({x} + a • t)) =ᶠ[𝓝[>] 0] fun r =>
    μ (s ∩ ({x} + r • t)) / μ ({x} + r • t)

Tactic:
filter_upwards [self_mem_nhdsWithin]

Result:
case h
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
inst✝¹ : FiniteDimensional ℝ E
μ : Measure E
inst✝ : μ.IsAddHaarMeasure
s : Set E
hs : MeasurableSet s
x : E
h : Tendsto (fun r => μ (s ∩ closedBall x r) / μ (closedBall x r)) (𝓝[>] 0) (𝓝 1)
t : Set E
ht : MeasurableSet t
h't : μ t ≠ 0
h''t : μ t ≠ ⊤
I : ∀ (u v : Set E), μ u ≠ 0 → μ u ≠ ⊤ → MeasurableSet v → μ u / μ u - μ (vᶜ ∩ u) / μ u = μ (v ∩ u) / μ u
L : Tendsto (fun r => μ (sᶜ ∩ closedBall x r) / μ (closedBall x r)) (𝓝[>] 0) (𝓝 0)
L' : Tendsto (fun r => μ (sᶜ ∩ ({x} + r • t)) / μ ({x} + r • t)) (𝓝[>] 0) (𝓝 0)
L'' : Tendsto (fun r => μ ({x} + r • t) / μ ({x} + r • t)) (𝓝[>] 0) (𝓝 1)
this : Tendsto (fun a => μ ({x} + a • t) / μ ({x} + a • t) - μ (sᶜ ∩ ({x} + a • t)) / μ ({x} + a • t)) (𝓝[>] 0) (𝓝 1)
⊢ ∀ a ∈ Ioi 0,
    μ ({x} + a • t) / μ ({x} + a • t) - μ (sᶜ ∩ ({x} + a • t)) / μ ({x} + a • t) =
      μ (s ∩ ({x} + a • t)) / μ ({x} + a • t)

Proof state:
case h
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
inst✝¹ : FiniteDimensional ℝ E
μ : Measure E
inst✝ : μ.IsAddHaarMeasure
s : Set E
hs : MeasurableSet s
x : E
h : Tendsto (fun r => μ (s ∩ closedBall x r) / μ (closedBall x r)) (𝓝[>] 0) (𝓝 1)
t : Set E
ht : MeasurableSet t
h't : μ t ≠ 0
h''t : μ t ≠ ⊤
I : ∀ (u v : Set E), μ u ≠ 0 → μ u ≠ ⊤ → MeasurableSet v → μ u / μ u - μ (vᶜ ∩ u) / μ u = μ (v ∩ u) / μ u
A : Tendsto (fun r => μ (closedBall x r) / μ (closedBall x r)) (𝓝[>] 0) (𝓝 1)
B :
  Tendsto (fun a => μ (closedBall x a) / μ (closedBall x a) - μ (s ∩ closedBall x a) / μ (closedBall x a)) (𝓝[>] 0)
    (𝓝 0)
⊢ ∀ a ∈ Ioi 0,
    μ (closedBall x a) / μ (closedBall x a) - μ (s ∩ closedBall x a) / μ (closedBall x a) =
      μ (sᶜ ∩ closedBall x a) / μ (closedBall x a)

Tactic:
rintro r (rpos : 0 < r)

Result:
case h
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
inst✝¹ : FiniteDimensional ℝ E
μ : Measure E
inst✝ : μ.IsAddHaarMeasure
s : Set E
hs : MeasurableSet s
x : E
h : Tendsto (fun r => μ (s ∩ closedBall x r) / μ (closedBall x r)) (𝓝[>] 0) (𝓝 1)
t : Set E
ht : MeasurableSet t
h't : μ t ≠ 0
h''t : μ t ≠ ⊤
I : ∀ (u v : Set E), μ u ≠ 0 → μ u ≠ ⊤ → MeasurableSet v → μ u / μ u - μ (vᶜ ∩ u) / μ u = μ (v ∩ u) / μ u
A : Tendsto (fun r => μ (closedBall x r) / μ (closedBall x r)) (𝓝[>] 0) (𝓝 1)
B :
  Tendsto (fun a => μ (closedBall x a) / μ (closedBall x a) - μ (s ∩ closedBall x a) / μ (closedBall x a)) (𝓝[>] 0)
    (𝓝 0)
r : ℝ
rpos : 0 < r
⊢ μ (closedBall x r) / μ (closedBall x r) - μ (s ∩ closedBall x r) / μ (closedBall x r) =
    μ (sᶜ ∩ closedBall x r) / μ (closedBall x r)

Proof state:
case h.h0
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
inst✝¹ : FiniteDimensional ℝ E
μ : Measure E
inst✝ : μ.IsAddHaarMeasure
s : Set E
hs : MeasurableSet s
x : E
h : Tendsto (fun r => μ (s ∩ closedBall x r) / μ (closedBall x r)) (𝓝[>] 0) (𝓝 1)
t : Set E
ht : MeasurableSet t
h't : μ t ≠ 0
h''t : μ t ≠ ⊤
I : ∀ (u v : Set E), μ u ≠ 0 → μ u ≠ ⊤ → MeasurableSet v → μ u / μ u - μ (vᶜ ∩ u) / μ u = μ (v ∩ u) / μ u
r : ℝ
hr : r ∈ Ioi 0
⊢ μ (closedBall x r) ≠ 0

Tactic:
exact (measure_closedBall_pos μ _ hr).ne'

Result:
no goals

Proof state:
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
inst✝¹ : FiniteDimensional ℝ E
μ : Measure E
inst✝ : μ.IsAddHaarMeasure
s : Set E
hs : MeasurableSet s
x : E
h : Tendsto (fun r => μ (s ∩ closedBall x r) / μ (closedBall x r)) (𝓝[>] 0) (𝓝 1)
t : Set E
ht : MeasurableSet t
h't : μ t ≠ 0
h''t : μ t ≠ ⊤
u v : Set E
uzero : μ u ≠ 0
utop : μ u ≠ ⊤
vmeas : MeasurableSet v
⊢ 0 < μ (vᶜ ∩ u) → μ (vᶜ ∩ u) < μ u → (μ u)⁻¹ ≠ ⊤

Tactic:
simp only [uzero, ENNReal.inv_eq_top, imp_true_iff, Ne, not_false_iff]

Result:
no goals

Proof state:
case h.ht
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
inst✝¹ : FiniteDimensional ℝ E
μ : Measure E
inst✝ : μ.IsAddHaarMeasure
s : Set E
hs : MeasurableSet s
x : E
h : Tendsto (fun r => μ (s ∩ closedBall x r) / μ (closedBall x r)) (𝓝[>] 0) (𝓝 1)
t : Set E
ht : MeasurableSet t
h't : μ t ≠ 0
h''t : μ t ≠ ⊤
I : ∀ (u v : Set E), μ u ≠ 0 → μ u ≠ ⊤ → MeasurableSet v → μ u / μ u - μ (vᶜ ∩ u) / μ u = μ (v ∩ u) / μ u
r : ℝ
hr : r ∈ Ioi 0
⊢ μ (closedBall x r) ≠ ⊤

Tactic:
exact measure_closedBall_lt_top.ne

Result:
no goals