Module: Mathlib.Probability.ProductMeasure

Goal state before:
pp: ι : Type u_1
X : ι → Type u_2
mX : (i : ι) → MeasurableSpace (X i)
μ : (i : ι) → Measure (X i)
hμ : ∀ (i : ι), IsProbabilityMeasure (μ i)
e : ℕ ≃ ι
I : Finset ι
S : Set ((i : ↥I) → X ↑i)
hS : MeasurableSet S
hs : cylinder I S ∈ measurableCylinders X
⊢ (Measure.pi fun i ↦ μ (e ↑i)) (⇑(Equiv.piCongrLeft (fun b ↦ X ↑b) (e.restrictPreimageFinset I)) ⁻¹' S) =
    (map (⇑(piCongrLeft (fun i ↦ X ↑i) (e.restrictPreimageFinset I)))
        (Measure.pi fun i ↦ μ ↑((e.restrictPreimageFinset I) i)))
      S

pp: case hf
ι : Type u_1
X : ι → Type u_2
mX : (i : ι) → MeasurableSpace (X i)
μ : (i : ι) → Measure (X i)
hμ : ∀ (i : ι), IsProbabilityMeasure (μ i)
e : ℕ ≃ ι
I : Finset ι
S : Set ((i : ↥I) → X ↑i)
hS : MeasurableSet S
hs : cylinder I S ∈ measurableCylinders X
⊢ Measurable (I.preimage ⇑e ⋯).restrict

pp: case hs
ι : Type u_1
X : ι → Type u_2
mX : (i : ι) → MeasurableSpace (X i)
μ : (i : ι) → Measure (X i)
hμ : ∀ (i : ι), IsProbabilityMeasure (μ i)
e : ℕ ≃ ι
I : Finset ι
S : Set ((i : ↥I) → X ↑i)
hS : MeasurableSet S
hs : cylinder I S ∈ measurableCylinders X
⊢ MeasurableSet (⇑(Equiv.piCongrLeft (fun b ↦ X ↑b) (e.restrictPreimageFinset I)) ⁻¹' S)

pp: ι : Type u_1
X : ι → Type u_2
mX : (i : ι) → MeasurableSpace (X i)
μ : (i : ι) → Measure (X i)
hμ : ∀ (i : ι), IsProbabilityMeasure (μ i)
e : ℕ ≃ ι
I : Finset ι
S : Set ((i : ↥I) → X ↑i)
hS : MeasurableSet S
hs : cylinder I S ∈ measurableCylinders X
⊢ Measurable ⇑(piCongrLeft X e)

Tactic:
map_apply _ hS,

Goal state after:
ι : Type u_1
X : ι → Type u_2
mX : (i : ι) → MeasurableSpace (X i)
μ : (i : ι) → Measure (X i)
hμ : ∀ (i : ι), IsProbabilityMeasure (μ i)
e : ℕ ≃ ι
I : Finset ι
S : Set ((i : ↥I) → X ↑i)
hS : MeasurableSet S
hs : cylinder I S ∈ measurableCylinders X
⊢ (Measure.pi fun i ↦ μ (e ↑i)) (⇑(Equiv.piCongrLeft (fun b ↦ X ↑b) (e.restrictPreimageFinset I)) ⁻¹' S) =
    (Measure.pi fun i ↦ μ ↑((e.restrictPreimageFinset I) i))
      (⇑(piCongrLeft (fun i ↦ X ↑i) (e.restrictPreimageFinset I)) ⁻¹' S)

ι : Type u_1
X : ι → Type u_2
mX : (i : ι) → MeasurableSpace (X i)
μ : (i : ι) → Measure (X i)
hμ : ∀ (i : ι), IsProbabilityMeasure (μ i)
e : ℕ ≃ ι
I : Finset ι
S : Set ((i : ↥I) → X ↑i)
hS : MeasurableSet S
hs : cylinder I S ∈ measurableCylinders X
⊢ Measurable ⇑(piCongrLeft (fun i ↦ X ↑i) (e.restrictPreimageFinset I))

case hf
ι : Type u_1
X : ι → Type u_2
mX : (i : ι) → MeasurableSpace (X i)
μ : (i : ι) → Measure (X i)
hμ : ∀ (i : ι), IsProbabilityMeasure (μ i)
e : ℕ ≃ ι
I : Finset ι
S : Set ((i : ↥I) → X ↑i)
hS : MeasurableSet S
hs : cylinder I S ∈ measurableCylinders X
⊢ Measurable (I.preimage ⇑e ⋯).restrict

case hs
ι : Type u_1
X : ι → Type u_2
mX : (i : ι) → MeasurableSpace (X i)
μ : (i : ι) → Measure (X i)
hμ : ∀ (i : ι), IsProbabilityMeasure (μ i)
e : ℕ ≃ ι
I : Finset ι
S : Set ((i : ↥I) → X ↑i)
hS : MeasurableSet S
hs : cylinder I S ∈ measurableCylinders X
⊢ MeasurableSet (⇑(Equiv.piCongrLeft (fun b ↦ X ↑b) (e.restrictPreimageFinset I)) ⁻¹' S)

ι : Type u_1
X : ι → Type u_2
mX : (i : ι) → MeasurableSpace (X i)
μ : (i : ι) → Measure (X i)
hμ : ∀ (i : ι), IsProbabilityMeasure (μ i)
e : ℕ ≃ ι
I : Finset ι
S : Set ((i : ↥I) → X ↑i)
hS : MeasurableSet S
hs : cylinder I S ∈ measurableCylinders X
⊢ Measurable ⇑(piCongrLeft X e)