-- Mathlib/Analysis/Calculus/Rademacher.lean
theorem ae_differentiableAt_of_real (hf : LipschitzWith C f) :
    ∀ᵐ x ∂μ, DifferentiableAt ℝ f x

Proof state:
case h.intro
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
C : ℝ≥0
f : E → ℝ
μ : Measure E
inst✝¹ : FiniteDimensional ℝ E
inst✝ : μ.IsAddHaarMeasure
hf : LipschitzWith C f
s : Set E
s_count : s.Countable
s_dense : Dense s
hs : sphere 0 1 ⊆ closure s
x : E
L : E →L[ℝ] ℝ
hL : ∀ v ∈ s, HasLineDerivAt ℝ f (L v) x v
⊢ DifferentiableAt ℝ f x

Tactic:
exact (hf.hasFDerivAt_of_hasLineDerivAt_of_closure hs hL).differentiableAt

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
C : ℝ≥0
f : E → ℝ
μ : Measure E
inst✝¹ : FiniteDimensional ℝ E
inst✝ : μ.IsAddHaarMeasure
hf : LipschitzWith C f
s : Set E
s_count : s.Countable
s_dense : Dense s
⊢ sphere 0 1 ⊆ univ

Tactic:
exact subset_univ _

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
C : ℝ≥0
f : E → ℝ
μ : Measure E
inst✝¹ : FiniteDimensional ℝ E
inst✝ : μ.IsAddHaarMeasure
hf : LipschitzWith C f
s : Set E
s_count : s.Countable
s_dense : Dense s
⊢ sphere 0 1 ⊆ closure s

Tactic:
rw [s_dense.closure_eq]

Result:
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
C : ℝ≥0
f : E → ℝ
μ : Measure E
inst✝¹ : FiniteDimensional ℝ E
inst✝ : μ.IsAddHaarMeasure
hf : LipschitzWith C f
s : Set E
s_count : s.Countable
s_dense : Dense s
⊢ sphere 0 1 ⊆ univ

Proof state:
case intro.intro
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
C : ℝ≥0
f : E → ℝ
μ : Measure E
inst✝¹ : FiniteDimensional ℝ E
inst✝ : μ.IsAddHaarMeasure
hf : LipschitzWith C f
s : Set E
s_count : s.Countable
s_dense : Dense s
⊢ ∀ᵐ (x : E) ∂μ, DifferentiableAt ℝ f x

Tactic:
have hs : sphere 0 1 ⊆ closure s := by rw [s_dense.closure_eq]; exact subset_univ _

Result:
case intro.intro
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
C : ℝ≥0
f : E → ℝ
μ : Measure E
inst✝¹ : FiniteDimensional ℝ E
inst✝ : μ.IsAddHaarMeasure
hf : LipschitzWith C f
s : Set E
s_count : s.Countable
s_dense : Dense s
hs : sphere 0 1 ⊆ closure s
⊢ ∀ᵐ (x : E) ∂μ, DifferentiableAt ℝ f x

Proof state:
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
C : ℝ≥0
f : E → ℝ
μ : Measure E
inst✝¹ : FiniteDimensional ℝ E
inst✝ : μ.IsAddHaarMeasure
hf : LipschitzWith C f
⊢ ∀ᵐ (x : E) ∂μ, DifferentiableAt ℝ f x

Tactic:
obtain ⟨s, s_count, s_dense⟩ : ∃ (s : Set E), s.Countable ∧ Dense s :=
  TopologicalSpace.exists_countable_dense E

Result:
case intro.intro
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
C : ℝ≥0
f : E → ℝ
μ : Measure E
inst✝¹ : FiniteDimensional ℝ E
inst✝ : μ.IsAddHaarMeasure
hf : LipschitzWith C f
s : Set E
s_count : s.Countable
s_dense : Dense s
⊢ ∀ᵐ (x : E) ∂μ, DifferentiableAt ℝ f x

Proof state:
case intro.intro
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
C : ℝ≥0
f : E → ℝ
μ : Measure E
inst✝¹ : FiniteDimensional ℝ E
inst✝ : μ.IsAddHaarMeasure
hf : LipschitzWith C f
s : Set E
s_count : s.Countable
s_dense : Dense s
hs : sphere 0 1 ⊆ closure s
⊢ ∀ᵐ (x : E) ∂μ, DifferentiableAt ℝ f x

Tactic:
filter_upwards [hf.ae_exists_fderiv_of_countable s_count]

Result:
case h
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
C : ℝ≥0
f : E → ℝ
μ : Measure E
inst✝¹ : FiniteDimensional ℝ E
inst✝ : μ.IsAddHaarMeasure
hf : LipschitzWith C f
s : Set E
s_count : s.Countable
s_dense : Dense s
hs : sphere 0 1 ⊆ closure s
⊢ ∀ (a : E), (∃ L, ∀ v ∈ s, HasLineDerivAt ℝ f (L v) a v) → DifferentiableAt ℝ f a

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
C : ℝ≥0
f : E → ℝ
μ : Measure E
inst✝¹ : FiniteDimensional ℝ E
inst✝ : μ.IsAddHaarMeasure
hf : LipschitzWith C f
s : Set E
s_count : s.Countable
s_dense : Dense s
hs : sphere 0 1 ⊆ closure s
⊢ ∀ (a : E), (∃ L, ∀ v ∈ s, HasLineDerivAt ℝ f (L v) a v) → DifferentiableAt ℝ f a

Tactic:
rintro x ⟨L, hL⟩

Result:
case h.intro
E : Type u_1
inst✝⁵ : NormedAddCommGroup E
inst✝⁴ : NormedSpace ℝ E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
C : ℝ≥0
f : E → ℝ
μ : Measure E
inst✝¹ : FiniteDimensional ℝ E
inst✝ : μ.IsAddHaarMeasure
hf : LipschitzWith C f
s : Set E
s_count : s.Countable
s_dense : Dense s
hs : sphere 0 1 ⊆ closure s
x : E
L : E →L[ℝ] ℝ
hL : ∀ v ∈ s, HasLineDerivAt ℝ f (L v) x v
⊢ DifferentiableAt ℝ f x