Theorem: MeasureTheory.Measure.pi_map_piOptionEquivProd
File: Mathlib/MeasureTheory/Constructions/Pi.lean

Proof steps:
state_before: ι : Type u_1
ι' : Type u_2
α : ι → Type u_3
inst✝⁴ : Fintype ι
m : (i : ι) → OuterMeasure (α i)
inst✝³ : (i : ι) → MeasurableSpace (α i)
μ✝ : (i : ι) → Measure (α i)
inst✝² : ∀ (i : ι), SigmaFinite (μ✝ i)
β : Option ι → Type u_4
inst✝¹ : (i : Option ι) → MeasurableSpace (β i)
μ : (i : Option ι) → Measure (β i)
inst✝ : ∀ (i : Option ι), SigmaFinite (μ i)
⊢ map (⇑(MeasurableEquiv.piOptionEquivProd β).symm) ((Measure.pi fun i => μ (some i)).prod (μ none)) = Measure.pi μ
state_after: ι : Type u_1
ι' : Type u_2
α : ι → Type u_3
inst✝⁴ : Fintype ι
m : (i : ι) → OuterMeasure (α i)
inst✝³ : (i : ι) → MeasurableSpace (α i)
μ✝ : (i : ι) → Measure (α i)
inst✝² : ∀ (i : ι), SigmaFinite (μ✝ i)
β : Option ι → Type u_4
inst✝¹ : (i : Option ι) → MeasurableSpace (β i)
μ : (i : Option ι) → Measure (β i)
inst✝ : ∀ (i : Option ι), SigmaFinite (μ i)
s : (i : Option ι) → Set (β i)
x✝ : ∀ (i : Option ι), MeasurableSet (s i)
⊢ (map (⇑(MeasurableEquiv.piOptionEquivProd β).symm) ((Measure.pi fun i => μ (some i)).prod (μ none))) (univ.pi s) =
    ∏ i : Option ι, (μ i) (s i)
tactic: refine pi_eq (fun s _ ↦ ?_) |>.symm
state_before: ι : Type u_1
ι' : Type u_2
α : ι → Type u_3
inst✝⁴ : Fintype ι
m : (i : ι) → OuterMeasure (α i)
inst✝³ : (i : ι) → MeasurableSpace (α i)
μ✝ : (i : ι) → Measure (α i)
inst✝² : ∀ (i : ι), SigmaFinite (μ✝ i)
β : Option ι → Type u_4
inst✝¹ : (i : Option ι) → MeasurableSpace (β i)
μ : (i : Option ι) → Measure (β i)
inst✝ : ∀ (i : Option ι), SigmaFinite (μ i)
s : (i : Option ι) → Set (β i)
x✝ : ∀ (i : Option ι), MeasurableSet (s i)
⊢ (map (⇑(MeasurableEquiv.piOptionEquivProd β).symm) ((Measure.pi fun i => μ (some i)).prod (μ none))) (univ.pi s) =
    ∏ i : Option ι, (μ i) (s i)
state_after: ι : Type u_1
ι' : Type u_2
α : ι → Type u_3
inst✝⁴ : Fintype ι
m : (i : ι) → OuterMeasure (α i)
inst✝³ : (i : ι) → MeasurableSpace (α i)
μ✝ : (i : ι) → Measure (α i)
inst✝² : ∀ (i : ι), SigmaFinite (μ✝ i)
β : Option ι → Type u_4
inst✝¹ : (i : Option ι) → MeasurableSpace (β i)
μ : (i : Option ι) → Measure (β i)
inst✝ : ∀ (i : Option ι), SigmaFinite (μ i)
s : (i : Option ι) → Set (β i)
x✝ : ∀ (i : Option ι), MeasurableSet (s i)
e_meas : ((i : ι) → β (some i)) × β none ≃ᵐ ((i : Option ι) → β i) := (MeasurableEquiv.piOptionEquivProd β).symm
⊢ (map (⇑(MeasurableEquiv.piOptionEquivProd β).symm) ((Measure.pi fun i => μ (some i)).prod (μ none))) (univ.pi s) =
    ∏ i : Option ι, (μ i) (s i)
tactic: let e_meas : ((i : ι) → β (some i)) × β none ≃ᵐ ((i : Option ι) → β i) :=
    MeasurableEquiv.piOptionEquivProd β |>.symm
state_before: ι : Type u_1
ι' : Type u_2
α : ι → Type u_3
inst✝⁴ : Fintype ι
m : (i : ι) → OuterMeasure (α i)
inst✝³ : (i : ι) → MeasurableSpace (α i)
μ✝ : (i : ι) → Measure (α i)
inst✝² : ∀ (i : ι), SigmaFinite (μ✝ i)
β : Option ι → Type u_4
inst✝¹ : (i : Option ι) → MeasurableSpace (β i)
μ : (i : Option ι) → Measure (β i)
inst✝ : ∀ (i : Option ι), SigmaFinite (μ i)
s : (i : Option ι) → Set (β i)
x✝ : ∀ (i : Option ι), MeasurableSet (s i)
e_meas : ((i : ι) → β (some i)) × β none ≃ᵐ ((i : Option ι) → β i) := (MeasurableEquiv.piOptionEquivProd β).symm
⊢ (map (⇑(MeasurableEquiv.piOptionEquivProd β).symm) ((Measure.pi fun i => μ (some i)).prod (μ none))) (univ.pi s) =
    ∏ i : Option ι, (μ i) (s i)
state_after: ι : Type u_1
ι' : Type u_2
α : ι → Type u_3
inst✝⁴ : Fintype ι
m : (i : ι) → OuterMeasure (α i)
inst✝³ : (i : ι) → MeasurableSpace (α i)
μ✝ : (i : ι) → Measure (α i)
inst✝² : ∀ (i : ι), SigmaFinite (μ✝ i)
β : Option ι → Type u_4
inst✝¹ : (i : Option ι) → MeasurableSpace (β i)
μ : (i : Option ι) → Measure (β i)
inst✝ : ∀ (i : Option ι), SigmaFinite (μ i)
s : (i : Option ι) → Set (β i)
x✝ : ∀ (i : Option ι), MeasurableSet (s i)
e_meas : ((i : ι) → β (some i)) × β none ≃ᵐ ((i : Option ι) → β i) := (MeasurableEquiv.piOptionEquivProd β).symm
me : MeasurableEmbedding ⇑e_meas
⊢ (map (⇑(MeasurableEquiv.piOptionEquivProd β).symm) ((Measure.pi fun i => μ (some i)).prod (μ none))) (univ.pi s) =
    ∏ i : Option ι, (μ i) (s i)
tactic: have me := MeasurableEquiv.measurableEmbedding e_meas
state_before: ι : Type u_1
ι' : Type u_2
α : ι → Type u_3
inst✝⁴ : Fintype ι
m : (i : ι) → OuterMeasure (α i)
inst✝³ : (i : ι) → MeasurableSpace (α i)
μ✝ : (i : ι) → Measure (α i)
inst✝² : ∀ (i : ι), SigmaFinite (μ✝ i)
β : Option ι → Type u_4
inst✝¹ : (i : Option ι) → MeasurableSpace (β i)
μ : (i : Option ι) → Measure (β i)
inst✝ : ∀ (i : Option ι), SigmaFinite (μ i)
s : (i : Option ι) → Set (β i)
x✝ : ∀ (i : Option ι), MeasurableSet (s i)
e_meas : ((i : ι) → β (some i)) × β none ≃ᵐ ((i : Option ι) → β i) := (MeasurableEquiv.piOptionEquivProd β).symm
me : MeasurableEmbedding ⇑e_meas
⊢ (map (⇑(MeasurableEquiv.piOptionEquivProd β).symm) ((Measure.pi fun i => μ (some i)).prod (μ none))) (univ.pi s) =
    ∏ i : Option ι, (μ i) (s i)
state_after: ι : Type u_1
ι' : Type u_2
α : ι → Type u_3
inst✝⁴ : Fintype ι
m : (i : ι) → OuterMeasure (α i)
inst✝³ : (i : ι) → MeasurableSpace (α i)
μ✝ : (i : ι) → Measure (α i)
inst✝² : ∀ (i : ι), SigmaFinite (μ✝ i)
β : Option ι → Type u_4
inst✝¹ : (i : Option ι) → MeasurableSpace (β i)
μ : (i : Option ι) → Measure (β i)
inst✝ : ∀ (i : Option ι), SigmaFinite (μ i)
s : (i : Option ι) → Set (β i)
x✝ : ∀ (i : Option ι), MeasurableSet (s i)
e_meas : ((i : ι) → β (some i)) × β none ≃ᵐ ((i : Option ι) → β i) := (MeasurableEquiv.piOptionEquivProd β).symm
me : MeasurableEmbedding ⇑e_meas
this : ⇑e_meas ⁻¹' univ.pi s = (univ.pi fun i => s (some i)) ×ˢ s none
⊢ (map (⇑(MeasurableEquiv.piOptionEquivProd β).symm) ((Measure.pi fun i => μ (some i)).prod (μ none))) (univ.pi s) =
    ∏ i : Option ι, (μ i) (s i)
tactic: have : e_meas ⁻¹' pi univ s = (pi univ (fun i ↦ s (some i))) ×ˢ (s none) := by
    ext x
    simp only [mem_preimage, Set.mem_pi, mem_univ, forall_true_left, mem_prod]
    refine ⟨by tauto, fun _ i ↦ ?_⟩
    rcases i <;> tauto
state_before: ι : Type u_1
ι' : Type u_2
α : ι → Type u_3
inst✝⁴ : Fintype ι
m : (i : ι) → OuterMeasure (α i)
inst✝³ : (i : ι) → MeasurableSpace (α i)
μ✝ : (i : ι) → Measure (α i)
inst✝² : ∀ (i : ι), SigmaFinite (μ✝ i)
β : Option ι → Type u_4
inst✝¹ : (i : Option ι) → MeasurableSpace (β i)
μ : (i : Option ι) → Measure (β i)
inst✝ : ∀ (i : Option ι), SigmaFinite (μ i)
s : (i : Option ι) → Set (β i)
x✝ : ∀ (i : Option ι), MeasurableSet (s i)
e_meas : ((i : ι) → β (some i)) × β none ≃ᵐ ((i : Option ι) → β i) := (MeasurableEquiv.piOptionEquivProd β).symm
me : MeasurableEmbedding ⇑e_meas
this : ⇑e_meas ⁻¹' univ.pi s = (univ.pi fun i => s (some i)) ×ˢ s none
⊢ (map (⇑(MeasurableEquiv.piOptionEquivProd β).symm) ((Measure.pi fun i => μ (some i)).prod (μ none))) (univ.pi s) =
    ∏ i : Option ι, (μ i) (s i)
state_after: no goals
tactic: simp only [me.map_apply, univ_option, le_eq_subset, Finset.prod_insertNone, this, prod_prod,
    pi_pi, mul_comm]