-- Mathlib/MeasureTheory/Function/ConditionalExpectation/Indicator.lean
theorem condExp_ae_eq_restrict_zero (hs : MeasurableSet[m] s) (hf : f =ᵐ[μ.restrict s] 0) :
    μ[f|m] =ᵐ[μ.restrict s] 0

Proof state:
case pos.refine_3
α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
μ : Measure α
f : α → E
s : Set α
hs : MeasurableSet s
hf : f =ᶠ[ae (μ.restrict s)] 0
hm : m ≤ m0
hμm this✝ : SigmaFinite (μ.trim hm)
this : SigmaFinite ((μ.restrict s).trim hm)
hf_int : Integrable f μ
t : Set α
ht : MeasurableSet t
a✝ : (μ.restrict s) t < ⊤
⊢ ∫ (x : α) in t, f x ∂μ.restrict s = ∫ (x : α) in t, 0 x ∂μ.restrict s

Tactic:
refine setIntegral_congr_ae (hm _ ht) ?_

Result:
case pos.refine_3
α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
μ : Measure α
f : α → E
s : Set α
hs : MeasurableSet s
hf : f =ᶠ[ae (μ.restrict s)] 0
hm : m ≤ m0
hμm this✝ : SigmaFinite (μ.trim hm)
this : SigmaFinite ((μ.restrict s).trim hm)
hf_int : Integrable f μ
t : Set α
ht : MeasurableSet t
a✝ : (μ.restrict s) t < ⊤
⊢ ∀ᵐ (x : α) ∂μ.restrict s, x ∈ t → f x = 0 x

Proof state:
case pos.refine_4
α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
μ : Measure α
f : α → E
s : Set α
hs : MeasurableSet s
hf : f =ᶠ[ae (μ.restrict s)] 0
hm : m ≤ m0
hμm this✝ : SigmaFinite (μ.trim hm)
this : SigmaFinite ((μ.restrict s).trim hm)
hf_int : Integrable f μ
⊢ AEStronglyMeasurable (μ[f|m]) (μ.restrict s)

Tactic:
exact stronglyMeasurable_condExp.aestronglyMeasurable

Result:
no goals

Proof state:
case pos
α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
μ : Measure α
f : α → E
s : Set α
hs : MeasurableSet s
hf : f =ᶠ[ae (μ.restrict s)] 0
hm : m ≤ m0
hμm this : SigmaFinite (μ.trim hm)
⊢ μ[f|m] =ᶠ[ae (μ.restrict s)] 0

Tactic:
have : SigmaFinite ((μ.restrict s).trim hm) := by
  rw [← restrict_trim hm _ hs]
  exact Restrict.sigmaFinite _ s

Result:
case pos
α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
μ : Measure α
f : α → E
s : Set α
hs : MeasurableSet s
hf : f =ᶠ[ae (μ.restrict s)] 0
hm : m ≤ m0
hμm this✝ : SigmaFinite (μ.trim hm)
this : SigmaFinite ((μ.restrict s).trim hm)
⊢ μ[f|m] =ᶠ[ae (μ.restrict s)] 0

Proof state:
case pos
α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
μ : Measure α
f : α → E
s : Set α
hs : MeasurableSet s
hf : f =ᶠ[ae (μ.restrict s)] 0
hm : m ≤ m0
⊢ μ[f|m] =ᶠ[ae (μ.restrict s)] 0

case neg
α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
μ : Measure α
f : α → E
s : Set α
hs : MeasurableSet s
hf : f =ᶠ[ae (μ.restrict s)] 0
hm : ¬m ≤ m0
⊢ μ[f|m] =ᶠ[ae (μ.restrict s)] 0

Tactic:
swap

Result:
case neg
α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
μ : Measure α
f : α → E
s : Set α
hs : MeasurableSet s
hf : f =ᶠ[ae (μ.restrict s)] 0
hm : ¬m ≤ m0
⊢ μ[f|m] =ᶠ[ae (μ.restrict s)] 0

case pos
α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
μ : Measure α
f : α → E
s : Set α
hs : MeasurableSet s
hf : f =ᶠ[ae (μ.restrict s)] 0
hm : m ≤ m0
⊢ μ[f|m] =ᶠ[ae (μ.restrict s)] 0

Proof state:
α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
μ : Measure α
f : α → E
s : Set α
hs : MeasurableSet s
hf : f =ᶠ[ae (μ.restrict s)] 0
hm : m ≤ m0
hμm this : SigmaFinite (μ.trim hm)
⊢ SigmaFinite ((μ.trim hm).restrict s)

Tactic:
exact Restrict.sigmaFinite _ s

Result:
no goals

Proof state:
case pos.refine_3
α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
μ : Measure α
f : α → E
s : Set α
hs : MeasurableSet s
hf : f =ᶠ[ae (μ.restrict s)] 0
hm : m ≤ m0
hμm this✝ : SigmaFinite (μ.trim hm)
this : SigmaFinite ((μ.restrict s).trim hm)
hf_int : Integrable f μ
t : Set α
ht : MeasurableSet t
a✝ : (μ.restrict s) t < ⊤
⊢ ∀ᵐ (x : α) ∂μ.restrict s, x ∈ t → f x = 0 x

Tactic:
filter_upwards [hf] with x hx _ using hx

Result:
no goals

Proof state:
case pos
α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
μ : Measure α
f : α → E
s : Set α
hs : MeasurableSet s
hf : f =ᶠ[ae (μ.restrict s)] 0
hm : m ≤ m0
hμm this✝ : SigmaFinite (μ.trim hm)
this : SigmaFinite ((μ.restrict s).trim hm)
hf_int : Integrable f μ
⊢ μ[f|m] =ᶠ[ae (μ.restrict s)] 0

case neg
α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
μ : Measure α
f : α → E
s : Set α
hs : MeasurableSet s
hf : f =ᶠ[ae (μ.restrict s)] 0
hm : m ≤ m0
hμm this✝ : SigmaFinite (μ.trim hm)
this : SigmaFinite ((μ.restrict s).trim hm)
hf_int : ¬Integrable f μ
⊢ μ[f|m] =ᶠ[ae (μ.restrict s)] 0

Tactic:
swap

Result:
case neg
α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
μ : Measure α
f : α → E
s : Set α
hs : MeasurableSet s
hf : f =ᶠ[ae (μ.restrict s)] 0
hm : m ≤ m0
hμm this✝ : SigmaFinite (μ.trim hm)
this : SigmaFinite ((μ.restrict s).trim hm)
hf_int : ¬Integrable f μ
⊢ μ[f|m] =ᶠ[ae (μ.restrict s)] 0

case pos
α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
μ : Measure α
f : α → E
s : Set α
hs : MeasurableSet s
hf : f =ᶠ[ae (μ.restrict s)] 0
hm : m ≤ m0
hμm this✝ : SigmaFinite (μ.trim hm)
this : SigmaFinite ((μ.restrict s).trim hm)
hf_int : Integrable f μ
⊢ μ[f|m] =ᶠ[ae (μ.restrict s)] 0

Proof state:
case neg
α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
μ : Measure α
f : α → E
s : Set α
hs : MeasurableSet s
hf : f =ᶠ[ae (μ.restrict s)] 0
hm : ¬m ≤ m0
⊢ μ[f|m] =ᶠ[ae (μ.restrict s)] 0

Tactic:
simp_rw [condExp_of_not_le hm]

Result:
case neg
α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
μ : Measure α
f : α → E
s : Set α
hs : MeasurableSet s
hf : f =ᶠ[ae (μ.restrict s)] 0
hm : ¬m ≤ m0
⊢ 0 =ᶠ[ae (μ.restrict s)] 0

Proof state:
case neg
α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
μ : Measure α
f : α → E
s : Set α
hs : MeasurableSet s
hf : f =ᶠ[ae (μ.restrict s)] 0
hm : m ≤ m0
hμm this✝ : SigmaFinite (μ.trim hm)
this : SigmaFinite ((μ.restrict s).trim hm)
hf_int : ¬Integrable f μ
⊢ μ[f|m] =ᶠ[ae (μ.restrict s)] 0

Tactic:
rw [condExp_of_not_integrable hf_int]

Result:
no goals

Proof state:
α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
μ : Measure α
f : α → E
s : Set α
hs : MeasurableSet s
hf : f =ᶠ[ae (μ.restrict s)] 0
⊢ μ[f|m] =ᶠ[ae (μ.restrict s)] 0

Tactic:
by_cases hm : m ≤ m0

Result:
case pos
α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
μ : Measure α
f : α → E
s : Set α
hs : MeasurableSet s
hf : f =ᶠ[ae (μ.restrict s)] 0
hm : m ≤ m0
⊢ μ[f|m] =ᶠ[ae (μ.restrict s)] 0

case neg
α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
μ : Measure α
f : α → E
s : Set α
hs : MeasurableSet s
hf : f =ᶠ[ae (μ.restrict s)] 0
hm : ¬m ≤ m0
⊢ μ[f|m] =ᶠ[ae (μ.restrict s)] 0