-- Mathlib/Analysis/Calculus/FDeriv/Measurable.lean
theorem measurableSet_of_differentiableAt_of_isComplete_with_param
    (hf : Continuous f.uncurry) {K : Set (E →L[𝕜] F)} (hK : IsComplete K) :
    MeasurableSet {p : α × E | DifferentiableAt 𝕜 (f p.1) p.2 ∧ fderiv 𝕜 (f p.1) p.2 ∈ K}

Proof state:
𝕜 : Type u_1
inst✝¹⁰ : NontriviallyNormedField 𝕜
E : Type u_2
inst✝⁹ : NormedAddCommGroup E
inst✝⁸ : NormedSpace 𝕜 E
inst✝⁷ : LocallyCompactSpace E
F : Type u_3
inst✝⁶ : NormedAddCommGroup F
inst✝⁵ : NormedSpace 𝕜 F
α : Type u_4
inst✝⁴ : TopologicalSpace α
f : α → E → F
inst✝³ : MeasurableSpace α
inst✝² : OpensMeasurableSpace α
inst✝¹ : MeasurableSpace E
inst✝ : OpensMeasurableSpace E
hf : Continuous (Function.uncurry f)
K : Set (E →L[𝕜] F)
hK : IsComplete K
this : {p | DifferentiableAt 𝕜 (f p.1) p.2 ∧ fderiv 𝕜 (f p.1) p.2 ∈ K} = {p | p.2 ∈ D (f p.1) K}
x✝² x✝¹ x✝ : ℕ
⊢ MeasurableSet
    (⋂ (_ : x✝ ≥ x✝¹), ⋂ i, ⋂ (_ : i ≥ x✝¹), {x | x.2 ∈ B (f x.1) K ((1 / 2) ^ x✝) ((1 / 2) ^ i) ((1 / 2) ^ x✝²)})

Tactic:
refine MeasurableSet.iInter (fun _ ↦ ?_)

Result:
𝕜 : Type u_1
inst✝¹⁰ : NontriviallyNormedField 𝕜
E : Type u_2
inst✝⁹ : NormedAddCommGroup E
inst✝⁸ : NormedSpace 𝕜 E
inst✝⁷ : LocallyCompactSpace E
F : Type u_3
inst✝⁶ : NormedAddCommGroup F
inst✝⁵ : NormedSpace 𝕜 F
α : Type u_4
inst✝⁴ : TopologicalSpace α
f : α → E → F
inst✝³ : MeasurableSpace α
inst✝² : OpensMeasurableSpace α
inst✝¹ : MeasurableSpace E
inst✝ : OpensMeasurableSpace E
hf : Continuous (Function.uncurry f)
K : Set (E →L[𝕜] F)
hK : IsComplete K
this : {p | DifferentiableAt 𝕜 (f p.1) p.2 ∧ fderiv 𝕜 (f p.1) p.2 ∈ K} = {p | p.2 ∈ D (f p.1) K}
x✝³ x✝² x✝¹ : ℕ
x✝ : x✝¹ ≥ x✝²
⊢ MeasurableSet (⋂ i, ⋂ (_ : i ≥ x✝²), {x | x.2 ∈ B (f x.1) K ((1 / 2) ^ x✝¹) ((1 / 2) ^ i) ((1 / 2) ^ x✝³)})

Proof state:
𝕜 : Type u_1
inst✝¹⁰ : NontriviallyNormedField 𝕜
E : Type u_2
inst✝⁹ : NormedAddCommGroup E
inst✝⁸ : NormedSpace 𝕜 E
inst✝⁷ : LocallyCompactSpace E
F : Type u_3
inst✝⁶ : NormedAddCommGroup F
inst✝⁵ : NormedSpace 𝕜 F
α : Type u_4
inst✝⁴ : TopologicalSpace α
f : α → E → F
inst✝³ : MeasurableSpace α
inst✝² : OpensMeasurableSpace α
inst✝¹ : MeasurableSpace E
inst✝ : OpensMeasurableSpace E
hf : Continuous (Function.uncurry f)
K : Set (E →L[𝕜] F)
hK : IsComplete K
this : {p | DifferentiableAt 𝕜 (f p.1) p.2 ∧ fderiv 𝕜 (f p.1) p.2 ∈ K} = {p | p.2 ∈ D (f p.1) K}
x✝³ x✝² x✝¹ : ℕ
x✝ : x✝¹ ≥ x✝²
⊢ MeasurableSet (⋂ i, ⋂ (_ : i ≥ x✝²), {x | x.2 ∈ B (f x.1) K ((1 / 2) ^ x✝¹) ((1 / 2) ^ i) ((1 / 2) ^ x✝³)})

Tactic:
refine MeasurableSet.iInter (fun _ ↦ ?_)

Result:
𝕜 : Type u_1
inst✝¹⁰ : NontriviallyNormedField 𝕜
E : Type u_2
inst✝⁹ : NormedAddCommGroup E
inst✝⁸ : NormedSpace 𝕜 E
inst✝⁷ : LocallyCompactSpace E
F : Type u_3
inst✝⁶ : NormedAddCommGroup F
inst✝⁵ : NormedSpace 𝕜 F
α : Type u_4
inst✝⁴ : TopologicalSpace α
f : α → E → F
inst✝³ : MeasurableSpace α
inst✝² : OpensMeasurableSpace α
inst✝¹ : MeasurableSpace E
inst✝ : OpensMeasurableSpace E
hf : Continuous (Function.uncurry f)
K : Set (E →L[𝕜] F)
hK : IsComplete K
this : {p | DifferentiableAt 𝕜 (f p.1) p.2 ∧ fderiv 𝕜 (f p.1) p.2 ∈ K} = {p | p.2 ∈ D (f p.1) K}
x✝⁴ x✝³ x✝² : ℕ
x✝¹ : x✝² ≥ x✝³
x✝ : ℕ
⊢ MeasurableSet (⋂ (_ : x✝ ≥ x✝³), {x | x.2 ∈ B (f x.1) K ((1 / 2) ^ x✝²) ((1 / 2) ^ x✝) ((1 / 2) ^ x✝⁴)})