Theorem: LipschitzOnWith.ae_differentiableWithinAt_of_mem
File: Mathlib/Analysis/Calculus/Rademacher.lean

Proof steps:
state_before: E : Type u_1
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedSpace ℝ E
inst✝⁶ : FiniteDimensional ℝ E
inst✝⁵ : MeasurableSpace E
inst✝⁴ : BorelSpace E
F : Type u_2
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace ℝ F
C D : ℝ≥0
f✝ g : E → ℝ
s : Set E
μ : Measure E
inst✝¹ : μ.IsAddHaarMeasure
inst✝ : FiniteDimensional ℝ F
f : E → F
hf : LipschitzOnWith C f s
⊢ ∀ᵐ (x : E) ∂μ, x ∈ s → DifferentiableWithinAt ℝ f s x
state_after: E : Type u_1
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedSpace ℝ E
inst✝⁶ : FiniteDimensional ℝ E
inst✝⁵ : MeasurableSpace E
inst✝⁴ : BorelSpace E
F : Type u_2
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace ℝ F
C D : ℝ≥0
f✝ g : E → ℝ
s : Set E
μ : Measure E
inst✝¹ : μ.IsAddHaarMeasure
inst✝ : FiniteDimensional ℝ F
f : E → F
hf : LipschitzOnWith C f s
A : F ≃L[ℝ] ↑(Basis.ofVectorSpaceIndex ℝ F) → ℝ
⊢ ∀ᵐ (x : E) ∂μ, x ∈ s → DifferentiableWithinAt ℝ f s x
tactic: have A := (Basis.ofVectorSpace ℝ F).equivFun.toContinuousLinearEquiv
state_before: E : Type u_1
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedSpace ℝ E
inst✝⁶ : FiniteDimensional ℝ E
inst✝⁵ : MeasurableSpace E
inst✝⁴ : BorelSpace E
F : Type u_2
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace ℝ F
C D : ℝ≥0
f✝ g : E → ℝ
s : Set E
μ : Measure E
inst✝¹ : μ.IsAddHaarMeasure
inst✝ : FiniteDimensional ℝ F
f : E → F
hf : LipschitzOnWith C f s
A : F ≃L[ℝ] ↑(Basis.ofVectorSpaceIndex ℝ F) → ℝ
⊢ ∀ᵐ (x : E) ∂μ, x ∈ s → DifferentiableWithinAt ℝ f s x
state_after: E : Type u_1
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedSpace ℝ E
inst✝⁶ : FiniteDimensional ℝ E
inst✝⁵ : MeasurableSpace E
inst✝⁴ : BorelSpace E
F : Type u_2
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace ℝ F
C D : ℝ≥0
f✝ g : E → ℝ
s : Set E
μ : Measure E
inst✝¹ : μ.IsAddHaarMeasure
inst✝ : FiniteDimensional ℝ F
f : E → F
hf : LipschitzOnWith C f s
A : F ≃L[ℝ] ↑(Basis.ofVectorSpaceIndex ℝ F) → ℝ
⊢ ∀ᵐ (x : E) ∂μ, x ∈ s → DifferentiableWithinAt ℝ (⇑A ∘ f) s x
tactic: suffices H : ∀ᵐ x ∂μ, x ∈ s → DifferentiableWithinAt ℝ (A ∘ f) s x by
    filter_upwards [H] with x hx xs
    have : f = (A.symm ∘ A) ∘ f := by
      simp only [ContinuousLinearEquiv.symm_comp_self, Function.id_comp]
    rw [this]
    exact A.symm.differentiableAt.comp_differentiableWithinAt x (hx xs)
state_before: E : Type u_1
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedSpace ℝ E
inst✝⁶ : FiniteDimensional ℝ E
inst✝⁵ : MeasurableSpace E
inst✝⁴ : BorelSpace E
F : Type u_2
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace ℝ F
C D : ℝ≥0
f✝ g : E → ℝ
s : Set E
μ : Measure E
inst✝¹ : μ.IsAddHaarMeasure
inst✝ : FiniteDimensional ℝ F
f : E → F
hf : LipschitzOnWith C f s
A : F ≃L[ℝ] ↑(Basis.ofVectorSpaceIndex ℝ F) → ℝ
⊢ ∀ᵐ (x : E) ∂μ, x ∈ s → DifferentiableWithinAt ℝ (⇑A ∘ f) s x
state_after: case hf
E : Type u_1
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedSpace ℝ E
inst✝⁶ : FiniteDimensional ℝ E
inst✝⁵ : MeasurableSpace E
inst✝⁴ : BorelSpace E
F : Type u_2
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace ℝ F
C D : ℝ≥0
f✝ g : E → ℝ
s : Set E
μ : Measure E
inst✝¹ : μ.IsAddHaarMeasure
inst✝ : FiniteDimensional ℝ F
f : E → F
hf : LipschitzOnWith C f s
A : F ≃L[ℝ] ↑(Basis.ofVectorSpaceIndex ℝ F) → ℝ
⊢ LipschitzOnWith ?C (⇑A ∘ f) s

case C
E : Type u_1
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedSpace ℝ E
inst✝⁶ : FiniteDimensional ℝ E
inst✝⁵ : MeasurableSpace E
inst✝⁴ : BorelSpace E
F : Type u_2
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace ℝ F
C D : ℝ≥0
f✝ g : E → ℝ
s : Set E
μ : Measure E
inst✝¹ : μ.IsAddHaarMeasure
inst✝ : FiniteDimensional ℝ F
f : E → F
hf : LipschitzOnWith C f s
A : F ≃L[ℝ] ↑(Basis.ofVectorSpaceIndex ℝ F) → ℝ
⊢ ℝ≥0
tactic: apply ae_differentiableWithinAt_of_mem_pi
state_before: case hf
E : Type u_1
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedSpace ℝ E
inst✝⁶ : FiniteDimensional ℝ E
inst✝⁵ : MeasurableSpace E
inst✝⁴ : BorelSpace E
F : Type u_2
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace ℝ F
C D : ℝ≥0
f✝ g : E → ℝ
s : Set E
μ : Measure E
inst✝¹ : μ.IsAddHaarMeasure
inst✝ : FiniteDimensional ℝ F
f : E → F
hf : LipschitzOnWith C f s
A : F ≃L[ℝ] ↑(Basis.ofVectorSpaceIndex ℝ F) → ℝ
⊢ LipschitzOnWith ?C (⇑A ∘ f) s

case C
E : Type u_1
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedSpace ℝ E
inst✝⁶ : FiniteDimensional ℝ E
inst✝⁵ : MeasurableSpace E
inst✝⁴ : BorelSpace E
F : Type u_2
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace ℝ F
C D : ℝ≥0
f✝ g : E → ℝ
s : Set E
μ : Measure E
inst✝¹ : μ.IsAddHaarMeasure
inst✝ : FiniteDimensional ℝ F
f : E → F
hf : LipschitzOnWith C f s
A : F ≃L[ℝ] ↑(Basis.ofVectorSpaceIndex ℝ F) → ℝ
⊢ ℝ≥0
state_after: no goals
tactic: exact A.lipschitz.comp_lipschitzOnWith hf