-- Mathlib/MeasureTheory/Function/Jacobian.lean
theorem addHaar_image_le_mul_of_det_lt (A : E →L[ℝ] E) {m : ℝ≥0}
    (hm : ENNReal.ofReal |A.det| < m) :
    ∀ᶠ δ in 𝓝[>] (0 : ℝ≥0),
      ∀ (s : Set E) (f : E → E), ApproximatesLinearOn f A s δ → μ (f '' s) ≤ m * μ s

Proof state:
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : FiniteDimensional ℝ E
inst✝² : MeasurableSpace E
inst✝¹ : BorelSpace E
μ : Measure E
inst✝ : μ.IsAddHaarMeasure
A : E →L[ℝ] E
m : ℝ≥0
hm : ENNReal.ofReal |A.det| < ↑m
d : ℝ≥0∞ := ENNReal.ofReal |A.det|
HC : IsCompact (⇑A '' closedBall 0 1)
L0 : Tendsto (fun ε => μ (cthickening ε (⇑A '' closedBall 0 1))) (𝓝[>] 0) (𝓝 (μ (⇑A '' closedBall 0 1)))
⊢ ∃ ε, μ (closedBall 0 ε + ⇑A '' closedBall 0 1) < ↑m * μ (closedBall 0 1) ∧ 0 < ε

Tactic:
have L1 :
  Tendsto (fun ε => μ (closedBall 0 ε + A '' closedBall 0 1)) (𝓝[>] 0)
    (𝓝 (μ (A '' closedBall 0 1))) := by
  apply L0.congr' _
  filter_upwards [self_mem_nhdsWithin] with r hr
  rw [← HC.add_closedBall_zero (le_of_lt hr), add_comm]

Result:
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : FiniteDimensional ℝ E
inst✝² : MeasurableSpace E
inst✝¹ : BorelSpace E
μ : Measure E
inst✝ : μ.IsAddHaarMeasure
A : E →L[ℝ] E
m : ℝ≥0
hm : ENNReal.ofReal |A.det| < ↑m
d : ℝ≥0∞ := ENNReal.ofReal |A.det|
HC : IsCompact (⇑A '' closedBall 0 1)
L0 : Tendsto (fun ε => μ (cthickening ε (⇑A '' closedBall 0 1))) (𝓝[>] 0) (𝓝 (μ (⇑A '' closedBall 0 1)))
L1 : Tendsto (fun ε => μ (closedBall 0 ε + ⇑A '' closedBall 0 1)) (𝓝[>] 0) (𝓝 (μ (⇑A '' closedBall 0 1)))
⊢ ∃ ε, μ (closedBall 0 ε + ⇑A '' closedBall 0 1) < ↑m * μ (closedBall 0 1) ∧ 0 < ε

Proof state:
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : FiniteDimensional ℝ E
inst✝² : MeasurableSpace E
inst✝¹ : BorelSpace E
μ : Measure E
inst✝ : μ.IsAddHaarMeasure
A : E →L[ℝ] E
m : ℝ≥0
hm : ENNReal.ofReal |A.det| < ↑m
d : ℝ≥0∞ := ENNReal.ofReal |A.det|
ε : ℝ
hε : μ (closedBall 0 ε + ⇑A '' closedBall 0 1) < ↑m * μ (closedBall 0 1)
εpos : 0 < ε
this✝ : Iio ⟨ε, ⋯⟩ ∈ 𝓝 0
δ : ℝ≥0
s : Set E
f : E → E
hf : ApproximatesLinearOn f A s δ
hδ : ↑δ < ε
x : E
r : ℝ
xs : x ∈ s
r0 : 0 ≤ r
K : f '' (s ∩ closedBall x r) ⊆ {f x} + r • (⇑A '' closedBall 0 1 + closedBall 0 ε)
this : ⇑A '' closedBall 0 r + closedBall (f x) (ε * r) = {f x} + r • (⇑A '' closedBall 0 1 + closedBall 0 ε)
⊢ ENNReal.ofReal (r ^ finrank ℝ E) * μ (⇑A '' closedBall 0 1 + closedBall 0 ε) ≤
    ENNReal.ofReal (r ^ finrank ℝ E) * (↑m * μ (closedBall 0 1))

Tactic:
rw [add_comm]

Result:
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : FiniteDimensional ℝ E
inst✝² : MeasurableSpace E
inst✝¹ : BorelSpace E
μ : Measure E
inst✝ : μ.IsAddHaarMeasure
A : E →L[ℝ] E
m : ℝ≥0
hm : ENNReal.ofReal |A.det| < ↑m
d : ℝ≥0∞ := ENNReal.ofReal |A.det|
ε : ℝ
hε : μ (closedBall 0 ε + ⇑A '' closedBall 0 1) < ↑m * μ (closedBall 0 1)
εpos : 0 < ε
this✝ : Iio ⟨ε, ⋯⟩ ∈ 𝓝 0
δ : ℝ≥0
s : Set E
f : E → E
hf : ApproximatesLinearOn f A s δ
hδ : ↑δ < ε
x : E
r : ℝ
xs : x ∈ s
r0 : 0 ≤ r
K : f '' (s ∩ closedBall x r) ⊆ {f x} + r • (⇑A '' closedBall 0 1 + closedBall 0 ε)
this : ⇑A '' closedBall 0 r + closedBall (f x) (ε * r) = {f x} + r • (⇑A '' closedBall 0 1 + closedBall 0 ε)
⊢ ENNReal.ofReal (r ^ finrank ℝ E) * μ (closedBall 0 ε + ⇑A '' closedBall 0 1) ≤
    ENNReal.ofReal (r ^ finrank ℝ E) * (↑m * μ (closedBall 0 1))

Proof state:
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : FiniteDimensional ℝ E
inst✝² : MeasurableSpace E
inst✝¹ : BorelSpace E
μ : Measure E
inst✝ : μ.IsAddHaarMeasure
A : E →L[ℝ] E
m : ℝ≥0
hm : ENNReal.ofReal |A.det| < ↑m
d : ℝ≥0∞ := ENNReal.ofReal |A.det|
HC : IsCompact (⇑A '' closedBall 0 1)
⊢ Tendsto (fun ε => μ (cthickening ε (⇑A '' closedBall 0 1))) (𝓝 0) (𝓝 (μ (⇑A '' closedBall 0 1)))

Tactic:
exact tendsto_measure_cthickening_of_isCompact HC

Result:
no goals

Proof state:
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : FiniteDimensional ℝ E
inst✝² : MeasurableSpace E
inst✝¹ : BorelSpace E
μ : Measure E
inst✝ : μ.IsAddHaarMeasure
A : E →L[ℝ] E
m : ℝ≥0
hm : ENNReal.ofReal |A.det| < ↑m
d : ℝ≥0∞ := ENNReal.ofReal |A.det|
ε : ℝ
hε : μ (closedBall 0 ε + ⇑A '' closedBall 0 1) < ↑m * μ (closedBall 0 1)
εpos : 0 < ε
this : Iio ⟨ε, ⋯⟩ ∈ 𝓝 0
δ : ℝ≥0
s : Set E
f : E → E
hf : ApproximatesLinearOn f A s δ
hδ : ↑δ < ε
x : E
r : ℝ
xs : x ∈ s
r0 : 0 ≤ r
z : E
zs : z ∈ s
zr : ‖z - x‖ ≤ r
⊢ ↑δ * ‖z - x‖ ≤ ε * r

Tactic:
gcongr

Result:
no goals

Proof state:
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : FiniteDimensional ℝ E
inst✝² : MeasurableSpace E
inst✝¹ : BorelSpace E
μ : Measure E
inst✝ : μ.IsAddHaarMeasure
A : E →L[ℝ] E
m : ℝ≥0
hm : ENNReal.ofReal |A.det| < ↑m
d : ℝ≥0∞ := ENNReal.ofReal |A.det|
ε : ℝ
hε : μ (closedBall 0 ε + ⇑A '' closedBall 0 1) < ↑m * μ (closedBall 0 1)
εpos : 0 < ε
this✝ : Iio ⟨ε, ⋯⟩ ∈ 𝓝 0
δ : ℝ≥0
s : Set E
f : E → E
hf : ApproximatesLinearOn f A s δ
hδ : ↑δ < ε
I : ∀ (x : E) (r : ℝ), x ∈ s → 0 ≤ r → μ (f '' (s ∩ closedBall x r)) ≤ ↑m * μ (closedBall x r)
a : ℝ≥0∞
ha : 0 < a
t : Set E
r : E → ℝ
t_count : t.Countable
ts : t ⊆ s
rpos : ∀ x ∈ t, 0 < r x
st : s ⊆ ⋃ x, closedBall (↑x) (r ↑x)
μt : ∑' (x : ↑t), μ (closedBall (↑x) (r ↑x)) ≤ μ s + a
this : Encodable ↑t
⊢ μ (f '' s) ≤ μ (⋃ x, f '' (s ∩ closedBall (↑x) (r ↑x)))

Tactic:
apply measure_mono

Result:
case h
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : FiniteDimensional ℝ E
inst✝² : MeasurableSpace E
inst✝¹ : BorelSpace E
μ : Measure E
inst✝ : μ.IsAddHaarMeasure
A : E →L[ℝ] E
m : ℝ≥0
hm : ENNReal.ofReal |A.det| < ↑m
d : ℝ≥0∞ := ENNReal.ofReal |A.det|
ε : ℝ
hε : μ (closedBall 0 ε + ⇑A '' closedBall 0 1) < ↑m * μ (closedBall 0 1)
εpos : 0 < ε
this✝ : Iio ⟨ε, ⋯⟩ ∈ 𝓝 0
δ : ℝ≥0
s : Set E
f : E → E
hf : ApproximatesLinearOn f A s δ
hδ : ↑δ < ε
I : ∀ (x : E) (r : ℝ), x ∈ s → 0 ≤ r → μ (f '' (s ∩ closedBall x r)) ≤ ↑m * μ (closedBall x r)
a : ℝ≥0∞
ha : 0 < a
t : Set E
r : E → ℝ
t_count : t.Countable
ts : t ⊆ s
rpos : ∀ x ∈ t, 0 < r x
st : s ⊆ ⋃ x, closedBall (↑x) (r ↑x)
μt : ∑' (x : ↑t), μ (closedBall (↑x) (r ↑x)) ≤ μ s + a
this : Encodable ↑t
⊢ f '' s ⊆ ⋃ x, f '' (s ∩ closedBall (↑x) (r ↑x))

Proof state:
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : FiniteDimensional ℝ E
inst✝² : MeasurableSpace E
inst✝¹ : BorelSpace E
μ : Measure E
inst✝ : μ.IsAddHaarMeasure
A : E →L[ℝ] E
m : ℝ≥0
hm : ENNReal.ofReal |A.det| < ↑m
d : ℝ≥0∞ := ENNReal.ofReal |A.det|
HC : IsCompact (⇑A '' closedBall 0 1)
L0 : Tendsto (fun ε => μ (cthickening ε (⇑A '' closedBall 0 1))) (𝓝[>] 0) (𝓝 (μ (⇑A '' closedBall 0 1)))
L1 : Tendsto (fun ε => μ (closedBall 0 ε + ⇑A '' closedBall 0 1)) (𝓝[>] 0) (𝓝 (μ (⇑A '' closedBall 0 1)))
L2 : Tendsto (fun ε => μ (closedBall 0 ε + ⇑A '' closedBall 0 1)) (𝓝[>] 0) (𝓝 (d * μ (closedBall 0 1)))
I : d * μ (closedBall 0 1) < ↑m * μ (closedBall 0 1)
H : ∀ᶠ (b : ℝ) in 𝓝[>] 0, μ (closedBall 0 b + ⇑A '' closedBall 0 1) < ↑m * μ (closedBall 0 1)
⊢ ∃ ε, μ (closedBall 0 ε + ⇑A '' closedBall 0 1) < ↑m * μ (closedBall 0 1) ∧ 0 < ε

Tactic:
exact (H.and self_mem_nhdsWithin).exists

Result:
no goals

Proof state:
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : FiniteDimensional ℝ E
inst✝² : MeasurableSpace E
inst✝¹ : BorelSpace E
μ : Measure E
inst✝ : μ.IsAddHaarMeasure
A : E →L[ℝ] E
m : ℝ≥0
hm : ENNReal.ofReal |A.det| < ↑m
d : ℝ≥0∞ := ENNReal.ofReal |A.det|
ε : ℝ
hε : μ (closedBall 0 ε + ⇑A '' closedBall 0 1) < ↑m * μ (closedBall 0 1)
εpos : 0 < ε
this : Iio ⟨ε, ⋯⟩ ∈ 𝓝 0
δ✝ : ℝ≥0
s : Set E
f : E → E
hf : ApproximatesLinearOn f A s δ✝
hδ : ↑δ✝ < ε
I : ∀ (x : E) (r : ℝ), x ∈ s → 0 ≤ r → μ (f '' (s ∩ closedBall x r)) ≤ ↑m * μ (closedBall x r)
a : ℝ≥0∞
ha : 0 < a
x : E
x✝ : x ∈ s
δ : ℝ
δpos : δ > 0
⊢ δ / 2 ∈ (fun x => Ioi 0) x ∩ Ioo 0 δ

Tactic:
simp [half_pos δpos, δpos]

Result:
no goals