-- Mathlib/Probability/Independence/ZeroOne.lean
theorem condExp_eq_zero_or_one_of_condIndepSet_self
    [StandardBorelSpace Ω]
    (hm : m ≤ m0) [hμ : IsFiniteMeasure μ] {t : Set Ω} (ht : MeasurableSet t)
    (h_indep : CondIndepSet m hm t t μ) :
    ∀ᵐ ω ∂μ, (μ⟦t | m⟧) ω = 0 ∨ (μ⟦t | m⟧) ω = 1

Proof state:
case h.inl
Ω : Type u_2
m m0 : MeasurableSpace Ω
μ : Measure Ω
inst✝ : StandardBorelSpace Ω
hm : m ≤ m0
hμ : IsFiniteMeasure μ
t : Set Ω
ht : MeasurableSet t
h_indep : CondIndepSet m hm t t μ
this : ∀ (a : Ω), IsFiniteMeasure ((condExpKernel μ m) a)
h✝ : ∀ᵐ (x : Ω) ∂μ, ((condExpKernel μ m) x) t = 0 ∨ ((condExpKernel μ m) x) t = 1
ω : Ω
hω_eq : (((condExpKernel μ m) ω) t).toReal = (μ[t.indicator fun ω => 1|m]) ω
h : ((condExpKernel μ m) ω) t = 0
⊢ (((condExpKernel μ m) ω) t = 0 ∨ ((condExpKernel μ m) ω) t = ⊤) ∨ ((condExpKernel μ m) ω) t = 1

Tactic:
exact Or.inl (Or.inl h)

Result:
no goals

Proof state:
Ω : Type u_2
m m0 : MeasurableSpace Ω
μ : Measure Ω
inst✝ : StandardBorelSpace Ω
hm : m ≤ m0
hμ : IsFiniteMeasure μ
t : Set Ω
ht : MeasurableSet t
h_indep : CondIndepSet m hm t t μ
⊢ ∀ᵐ (ω : Ω) ∂μ, (μ[t.indicator fun ω => 1|m]) ω = 0 ∨ (μ[t.indicator fun ω => 1|m]) ω = 1

Tactic:
have (a) : IsFiniteMeasure (condExpKernel μ m a) := inferInstance

Result:
Ω : Type u_2
m m0 : MeasurableSpace Ω
μ : Measure Ω
inst✝ : StandardBorelSpace Ω
hm : m ≤ m0
hμ : IsFiniteMeasure μ
t : Set Ω
ht : MeasurableSet t
h_indep : CondIndepSet m hm t t μ
this : ∀ (a : Ω), IsFiniteMeasure ((condExpKernel μ m) a)
⊢ ∀ᵐ (ω : Ω) ∂μ, (μ[t.indicator fun ω => 1|m]) ω = 0 ∨ (μ[t.indicator fun ω => 1|m]) ω = 1

Proof state:
case h
Ω : Type u_2
m m0 : MeasurableSpace Ω
μ : Measure Ω
inst✝ : StandardBorelSpace Ω
hm : m ≤ m0
hμ : IsFiniteMeasure μ
t : Set Ω
ht : MeasurableSet t
h_indep : CondIndepSet m hm t t μ
this : ∀ (a : Ω), IsFiniteMeasure ((condExpKernel μ m) a)
h : ∀ᵐ (x : Ω) ∂μ, ((condExpKernel μ m) x) t = 0 ∨ ((condExpKernel μ m) x) t = 1
ω : Ω
hω_eq : (((condExpKernel μ m) ω) t).toReal = (μ[t.indicator fun ω => 1|m]) ω
hω : ((condExpKernel μ m) ω) t = 0 ∨ ((condExpKernel μ m) ω) t = 1
⊢ (μ[t.indicator fun ω => 1|m]) ω = 0 ∨ (μ[t.indicator fun ω => 1|m]) ω = 1

Tactic:
rw [← hω_eq, ENNReal.toReal_eq_zero_iff, ENNReal.toReal_eq_one_iff]

Result:
case h
Ω : Type u_2
m m0 : MeasurableSpace Ω
μ : Measure Ω
inst✝ : StandardBorelSpace Ω
hm : m ≤ m0
hμ : IsFiniteMeasure μ
t : Set Ω
ht : MeasurableSet t
h_indep : CondIndepSet m hm t t μ
this : ∀ (a : Ω), IsFiniteMeasure ((condExpKernel μ m) a)
h : ∀ᵐ (x : Ω) ∂μ, ((condExpKernel μ m) x) t = 0 ∨ ((condExpKernel μ m) x) t = 1
ω : Ω
hω_eq : (((condExpKernel μ m) ω) t).toReal = (μ[t.indicator fun ω => 1|m]) ω
hω : ((condExpKernel μ m) ω) t = 0 ∨ ((condExpKernel μ m) ω) t = 1
⊢ (((condExpKernel μ m) ω) t = 0 ∨ ((condExpKernel μ m) ω) t = ⊤) ∨ ((condExpKernel μ m) ω) t = 1

Proof state:
Ω : Type u_2
m m0 : MeasurableSpace Ω
μ : Measure Ω
inst✝ : StandardBorelSpace Ω
hm : m ≤ m0
hμ : IsFiniteMeasure μ
t : Set Ω
ht : MeasurableSet t
h_indep : CondIndepSet m hm t t μ
this : ∀ (a : Ω), IsFiniteMeasure ((condExpKernel μ m) a)
h : ∀ᵐ (x : Ω) ∂μ, ((condExpKernel μ m) x) t = 0 ∨ ((condExpKernel μ m) x) t = 1
⊢ ∀ᵐ (ω : Ω) ∂μ, (μ[t.indicator fun ω => 1|m]) ω = 0 ∨ (μ[t.indicator fun ω => 1|m]) ω = 1

Tactic:
filter_upwards [condExpKernel_ae_eq_condExp hm ht, h] with ω hω_eq hω

Result:
case h
Ω : Type u_2
m m0 : MeasurableSpace Ω
μ : Measure Ω
inst✝ : StandardBorelSpace Ω
hm : m ≤ m0
hμ : IsFiniteMeasure μ
t : Set Ω
ht : MeasurableSet t
h_indep : CondIndepSet m hm t t μ
this : ∀ (a : Ω), IsFiniteMeasure ((condExpKernel μ m) a)
h : ∀ᵐ (x : Ω) ∂μ, ((condExpKernel μ m) x) t = 0 ∨ ((condExpKernel μ m) x) t = 1
ω : Ω
hω_eq : (((condExpKernel μ m) ω) t).toReal = (μ[t.indicator fun ω => 1|m]) ω
hω : ((condExpKernel μ m) ω) t = 0 ∨ ((condExpKernel μ m) ω) t = 1
⊢ (μ[t.indicator fun ω => 1|m]) ω = 0 ∨ (μ[t.indicator fun ω => 1|m]) ω = 1

Proof state:
case h.inr
Ω : Type u_2
m m0 : MeasurableSpace Ω
μ : Measure Ω
inst✝ : StandardBorelSpace Ω
hm : m ≤ m0
hμ : IsFiniteMeasure μ
t : Set Ω
ht : MeasurableSet t
h_indep : CondIndepSet m hm t t μ
this : ∀ (a : Ω), IsFiniteMeasure ((condExpKernel μ m) a)
h✝ : ∀ᵐ (x : Ω) ∂μ, ((condExpKernel μ m) x) t = 0 ∨ ((condExpKernel μ m) x) t = 1
ω : Ω
hω_eq : (((condExpKernel μ m) ω) t).toReal = (μ[t.indicator fun ω => 1|m]) ω
h : ((condExpKernel μ m) ω) t = 1
⊢ (((condExpKernel μ m) ω) t = 0 ∨ ((condExpKernel μ m) ω) t = ⊤) ∨ ((condExpKernel μ m) ω) t = 1

Tactic:
exact Or.inr h

Result:
no goals

Proof state:
case h
Ω : Type u_2
m m0 : MeasurableSpace Ω
μ : Measure Ω
inst✝ : StandardBorelSpace Ω
hm : m ≤ m0
hμ : IsFiniteMeasure μ
t : Set Ω
ht : MeasurableSet t
h_indep : CondIndepSet m hm t t μ
this : ∀ (a : Ω), IsFiniteMeasure ((condExpKernel μ m) a)
h : ∀ᵐ (x : Ω) ∂μ, ((condExpKernel μ m) x) t = 0 ∨ ((condExpKernel μ m) x) t = 1
ω : Ω
hω_eq : (((condExpKernel μ m) ω) t).toReal = (μ[t.indicator fun ω => 1|m]) ω
hω : ((condExpKernel μ m) ω) t = 0 ∨ ((condExpKernel μ m) ω) t = 1
⊢ (((condExpKernel μ m) ω) t = 0 ∨ ((condExpKernel μ m) ω) t = ⊤) ∨ ((condExpKernel μ m) ω) t = 1

Tactic:
cases hω with
| inl h => exact Or.inl (Or.inl h)
| inr h => exact Or.inr h

Result:
no goals

Proof state:
Ω : Type u_2
m m0 : MeasurableSpace Ω
μ : Measure Ω
inst✝ : StandardBorelSpace Ω
hm : m ≤ m0
hμ : IsFiniteMeasure μ
t : Set Ω
ht : MeasurableSet t
h_indep : CondIndepSet m hm t t μ
this : ∀ (a : Ω), IsFiniteMeasure ((condExpKernel μ m) a)
⊢ ∀ᵐ (ω : Ω) ∂μ, (μ[t.indicator fun ω => 1|m]) ω = 0 ∨ (μ[t.indicator fun ω => 1|m]) ω = 1

Tactic:
have h := ae_of_ae_trim hm (Kernel.measure_eq_zero_or_one_of_indepSet_self h_indep)

Result:
Ω : Type u_2
m m0 : MeasurableSpace Ω
μ : Measure Ω
inst✝ : StandardBorelSpace Ω
hm : m ≤ m0
hμ : IsFiniteMeasure μ
t : Set Ω
ht : MeasurableSet t
h_indep : CondIndepSet m hm t t μ
this : ∀ (a : Ω), IsFiniteMeasure ((condExpKernel μ m) a)
h : ∀ᵐ (x : Ω) ∂μ, ((condExpKernel μ m) x) t = 0 ∨ ((condExpKernel μ m) x) t = 1
⊢ ∀ᵐ (ω : Ω) ∂μ, (μ[t.indicator fun ω => 1|m]) ω = 0 ∨ (μ[t.indicator fun ω => 1|m]) ω = 1