-- Mathlib/Probability/Independence/Kernel.lean
theorem iIndepSets.iIndep (m : ι → MeasurableSpace Ω)
    (h_le : ∀ i, m i ≤ _mΩ) (π : ι → Set (Set Ω)) (h_pi : ∀ n, IsPiSystem (π n))
    (h_generate : ∀ i, m i = generateFrom (π i)) (h_ind : iIndepSets π κ μ) :
    iIndep m κ μ

Proof state:
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
m : ι → MeasurableSpace Ω
h_le : ∀ (i : ι), m i ≤ _mΩ
π : ι → Set (Set Ω)
h_pi : ∀ (n : ι), IsPiSystem (π n)
h_generate : ∀ (i : ι), m i = generateFrom (π i)
h_ind : iIndepSets π κ μ
hμ : μ ≠ 0
η : Kernel α Ω
η_eq : ⇑κ =ᶠ[ae μ] ⇑η
hη : IsMarkovKernel η
s : Finset ι
f : ι → Set Ω
a : ι
S : Finset ι
ha_notin_S : a ∉ S
h_rec : (∀ i ∈ S, f i ∈ (fun x => {s | MeasurableSet s}) i) → ∀ᵐ (a : α) ∂μ, (η a) (⋂ i ∈ S, f i) = ∏ i ∈ S, (η a) (f i)
hf_m : ∀ i ∈ insert a S, f i ∈ (fun x => {s | MeasurableSet s}) i
hf_m_S : ∀ x ∈ S, MeasurableSet (f x)
p : Set (Set Ω) := piiUnionInter π ↑S
m_p : MeasurableSpace Ω := generateFrom p
hS_eq_generate : m_p = generateFrom p
hp : IsPiSystem p
h_le' : ∀ (i : ι), generateFrom (π i) ≤ _mΩ
hm_p : m_p ≤ _mΩ
⊢ Indep m_p (m a) η μ

Tactic:
exact IndepSets.indep hm_p (h_le a) hp (h_pi a) hS_eq_generate (h_generate a)
  (iIndepSets.piiUnionInter_of_not_mem (h_ind.congr η_eq) ha_notin_S)

Result:
no goals

Proof state:
case inr.intro.intro.refine_2.refine_1
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
m : ι → MeasurableSpace Ω
h_le : ∀ (i : ι), m i ≤ _mΩ
π : ι → Set (Set Ω)
h_pi : ∀ (n : ι), IsPiSystem (π n)
h_generate : ∀ (i : ι), m i = generateFrom (π i)
h_ind : iIndepSets π κ μ
hμ : μ ≠ 0
η : Kernel α Ω
η_eq : ⇑κ =ᶠ[ae μ] ⇑η
hη : IsMarkovKernel η
s : Finset ι
f : ι → Set Ω
a : ι
S : Finset ι
ha_notin_S : a ∉ S
h_rec : (∀ i ∈ S, f i ∈ (fun x => {s | MeasurableSet s}) i) → ∀ᵐ (a : α) ∂μ, (η a) (⋂ i ∈ S, f i) = ∏ i ∈ S, (η a) (f i)
hf_m : ∀ i ∈ insert a S, f i ∈ (fun x => {s | MeasurableSet s}) i
hf_m_S : ∀ x ∈ S, MeasurableSet (f x)
p : Set (Set Ω) := piiUnionInter π ↑S
m_p : MeasurableSpace Ω := generateFrom p
hS_eq_generate : m_p = generateFrom p
h_indep : Indep m_p (m a) η μ
h_le_p : ∀ i ∈ S, m i ≤ m_p
h_S_f : ∀ i ∈ S, MeasurableSet (f i)
⊢ ⋂ n ∈ S, f n ∈ {s | MeasurableSet s}

Tactic:
exact S.measurableSet_biInter h_S_f

Result:
no goals

Proof state:
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
m : ι → MeasurableSpace Ω
h_le : ∀ (i : ι), m i ≤ _mΩ
π : ι → Set (Set Ω)
h_pi : ∀ (n : ι), IsPiSystem (π n)
h_generate : ∀ (i : ι), m i = generateFrom (π i)
h_ind : iIndepSets π κ μ
⊢ Kernel.iIndep m κ μ

Tactic:
rcases eq_or_ne μ 0 with rfl | hμ

Result:
case inl
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
m : ι → MeasurableSpace Ω
h_le : ∀ (i : ι), m i ≤ _mΩ
π : ι → Set (Set Ω)
h_pi : ∀ (n : ι), IsPiSystem (π n)
h_generate : ∀ (i : ι), m i = generateFrom (π i)
h_ind : iIndepSets π κ 0
⊢ Kernel.iIndep m κ 0

case inr
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
m : ι → MeasurableSpace Ω
h_le : ∀ (i : ι), m i ≤ _mΩ
π : ι → Set (Set Ω)
h_pi : ∀ (n : ι), IsPiSystem (π n)
h_generate : ∀ (i : ι), m i = generateFrom (π i)
h_ind : iIndepSets π κ μ
hμ : μ ≠ 0
⊢ Kernel.iIndep m κ μ

Proof state:
case inl
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
m : ι → MeasurableSpace Ω
h_le : ∀ (i : ι), m i ≤ _mΩ
π : ι → Set (Set Ω)
h_pi : ∀ (n : ι), IsPiSystem (π n)
h_generate : ∀ (i : ι), m i = generateFrom (π i)
h_ind : iIndepSets π κ 0
⊢ Kernel.iIndep m κ 0

Tactic:
simp

Result:
no goals

Proof state:
case inr.intro.intro.refine_2
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
m : ι → MeasurableSpace Ω
h_le : ∀ (i : ι), m i ≤ _mΩ
π : ι → Set (Set Ω)
h_pi : ∀ (n : ι), IsPiSystem (π n)
h_generate : ∀ (i : ι), m i = generateFrom (π i)
h_ind : iIndepSets π κ μ
hμ : μ ≠ 0
η : Kernel α Ω
η_eq : ⇑κ =ᶠ[ae μ] ⇑η
hη : IsMarkovKernel η
s : Finset ι
f : ι → Set Ω
a : ι
S : Finset ι
ha_notin_S : a ∉ S
h_rec : (∀ i ∈ S, f i ∈ (fun x => {s | MeasurableSet s}) i) → ∀ᵐ (a : α) ∂μ, (η a) (⋂ i ∈ S, f i) = ∏ i ∈ S, (η a) (f i)
hf_m : ∀ i ∈ insert a S, f i ∈ (fun x => {s | MeasurableSet s}) i
hf_m_S : ∀ x ∈ S, MeasurableSet (f x)
p : Set (Set Ω) := piiUnionInter π ↑S
m_p : MeasurableSpace Ω := generateFrom p
hS_eq_generate : m_p = generateFrom p
⊢ ∀ᵐ (a_1 : α) ∂μ, (η a_1) (⋂ i ∈ insert a S, f i) = ∏ i ∈ insert a S, (η a_1) (f i)

Tactic:
have h_indep : Indep m_p (m a) η μ := by
  have hp : IsPiSystem p := isPiSystem_piiUnionInter π h_pi S
  have h_le' : ∀ i, generateFrom (π i) ≤ _mΩ := fun i ↦ (h_generate i).symm.trans_le (h_le i)
  have hm_p : m_p ≤ _mΩ := generateFrom_piiUnionInter_le π h_le' S
  exact IndepSets.indep hm_p (h_le a) hp (h_pi a) hS_eq_generate (h_generate a)
    (iIndepSets.piiUnionInter_of_not_mem (h_ind.congr η_eq) ha_notin_S)

Result:
case inr.intro.intro.refine_2
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
m : ι → MeasurableSpace Ω
h_le : ∀ (i : ι), m i ≤ _mΩ
π : ι → Set (Set Ω)
h_pi : ∀ (n : ι), IsPiSystem (π n)
h_generate : ∀ (i : ι), m i = generateFrom (π i)
h_ind : iIndepSets π κ μ
hμ : μ ≠ 0
η : Kernel α Ω
η_eq : ⇑κ =ᶠ[ae μ] ⇑η
hη : IsMarkovKernel η
s : Finset ι
f : ι → Set Ω
a : ι
S : Finset ι
ha_notin_S : a ∉ S
h_rec : (∀ i ∈ S, f i ∈ (fun x => {s | MeasurableSet s}) i) → ∀ᵐ (a : α) ∂μ, (η a) (⋂ i ∈ S, f i) = ∏ i ∈ S, (η a) (f i)
hf_m : ∀ i ∈ insert a S, f i ∈ (fun x => {s | MeasurableSet s}) i
hf_m_S : ∀ x ∈ S, MeasurableSet (f x)
p : Set (Set Ω) := piiUnionInter π ↑S
m_p : MeasurableSpace Ω := generateFrom p
hS_eq_generate : m_p = generateFrom p
h_indep : Indep m_p (m a) η μ
⊢ ∀ᵐ (a_1 : α) ∂μ, (η a_1) (⋂ i ∈ insert a S, f i) = ∏ i ∈ insert a S, (η a_1) (f i)

Proof state:
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
m : ι → MeasurableSpace Ω
h_le : ∀ (i : ι), m i ≤ _mΩ
π : ι → Set (Set Ω)
h_pi : ∀ (n : ι), IsPiSystem (π n)
h_generate : ∀ (i : ι), m i = generateFrom (π i)
h_ind : iIndepSets π κ μ
hμ : μ ≠ 0
η : Kernel α Ω
η_eq : ⇑κ =ᶠ[ae μ] ⇑η
hη : IsMarkovKernel η
s : Finset ι
f : ι → Set Ω
a : ι
S : Finset ι
ha_notin_S : a ∉ S
h_rec : (∀ i ∈ S, f i ∈ (fun x => {s | MeasurableSet s}) i) → ∀ᵐ (a : α) ∂μ, (η a) (⋂ i ∈ S, f i) = ∏ i ∈ S, (η a) (f i)
hf_m : ∀ i ∈ insert a S, f i ∈ (fun x => {s | MeasurableSet s}) i
hf_m_S : ∀ x ∈ S, MeasurableSet (f x)
p : Set (Set Ω) := piiUnionInter π ↑S
m_p : MeasurableSpace Ω := generateFrom p
hS_eq_generate : m_p = generateFrom p
h_indep : Indep m_p (m a) η μ
⊢ ∀ i ∈ S, m i ≤ m_p

Tactic:
intros n hn

Result:
α : Type u_1
Ω : Type u_2
ι : Type u_3
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : Kernel α Ω
μ : Measure α
m : ι → MeasurableSpace Ω
h_le : ∀ (i : ι), m i ≤ _mΩ
π : ι → Set (Set Ω)
h_pi : ∀ (n : ι), IsPiSystem (π n)
h_generate : ∀ (i : ι), m i = generateFrom (π i)
h_ind : iIndepSets π κ μ
hμ : μ ≠ 0
η : Kernel α Ω
η_eq : ⇑κ =ᶠ[ae μ] ⇑η
hη : IsMarkovKernel η
s : Finset ι
f : ι → Set Ω
a : ι
S : Finset ι
ha_notin_S : a ∉ S
h_rec : (∀ i ∈ S, f i ∈ (fun x => {s | MeasurableSet s}) i) → ∀ᵐ (a : α) ∂μ, (η a) (⋂ i ∈ S, f i) = ∏ i ∈ S, (η a) (f i)
hf_m : ∀ i ∈ insert a S, f i ∈ (fun x => {s | MeasurableSet s}) i
hf_m_S : ∀ x ∈ S, MeasurableSet (f x)
p : Set (Set Ω) := piiUnionInter π ↑S
m_p : MeasurableSpace Ω := generateFrom p
hS_eq_generate : m_p = generateFrom p
h_indep : Indep m_p (m a) η μ
n : ι
hn : n ∈ S
⊢ m n ≤ m_p