Theorem: MeasureTheory.AEFinStronglyMeasurable.exists_set_sigmaFinite
File: Mathlib/MeasureTheory/Function/StronglyMeasurable/Basic.lean

Proof steps:
state_before: α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
inst✝³ : Countable ι
m : MeasurableSpace α
μ : Measure α
inst✝² : TopologicalSpace β
f g : α → β
inst✝¹ : Zero β
inst✝ : T2Space β
hf : AEFinStronglyMeasurable f μ
⊢ ∃ t, MeasurableSet t ∧ f =ᶠ[ae (μ.restrict tᶜ)] 0 ∧ SigmaFinite (μ.restrict t)
state_after: case intro.intro
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
inst✝³ : Countable ι
m : MeasurableSpace α
μ : Measure α
inst✝² : TopologicalSpace β
f g✝ : α → β
inst✝¹ : Zero β
inst✝ : T2Space β
g : α → β
hg : FinStronglyMeasurable g μ
hfg : f =ᶠ[ae μ] g
⊢ ∃ t, MeasurableSet t ∧ f =ᶠ[ae (μ.restrict tᶜ)] 0 ∧ SigmaFinite (μ.restrict t)
tactic: rcases hf with ⟨g, hg, hfg⟩
state_before: case intro.intro
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
inst✝³ : Countable ι
m : MeasurableSpace α
μ : Measure α
inst✝² : TopologicalSpace β
f g✝ : α → β
inst✝¹ : Zero β
inst✝ : T2Space β
g : α → β
hg : FinStronglyMeasurable g μ
hfg : f =ᶠ[ae μ] g
⊢ ∃ t, MeasurableSet t ∧ f =ᶠ[ae (μ.restrict tᶜ)] 0 ∧ SigmaFinite (μ.restrict t)
state_after: case intro.intro.intro.intro.intro
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
inst✝³ : Countable ι
m : MeasurableSpace α
μ : Measure α
inst✝² : TopologicalSpace β
f g✝ : α → β
inst✝¹ : Zero β
inst✝ : T2Space β
g : α → β
hg : FinStronglyMeasurable g μ
hfg : f =ᶠ[ae μ] g
t : Set α
ht : MeasurableSet t
hgt_zero : ∀ x ∈ tᶜ, g x = 0
htμ : SigmaFinite (μ.restrict t)
⊢ ∃ t, MeasurableSet t ∧ f =ᶠ[ae (μ.restrict tᶜ)] 0 ∧ SigmaFinite (μ.restrict t)
tactic: obtain ⟨t, ht, hgt_zero, htμ⟩ := hg.exists_set_sigmaFinite
state_before: case intro.intro.intro.intro.intro
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
inst✝³ : Countable ι
m : MeasurableSpace α
μ : Measure α
inst✝² : TopologicalSpace β
f g✝ : α → β
inst✝¹ : Zero β
inst✝ : T2Space β
g : α → β
hg : FinStronglyMeasurable g μ
hfg : f =ᶠ[ae μ] g
t : Set α
ht : MeasurableSet t
hgt_zero : ∀ x ∈ tᶜ, g x = 0
htμ : SigmaFinite (μ.restrict t)
⊢ ∃ t, MeasurableSet t ∧ f =ᶠ[ae (μ.restrict tᶜ)] 0 ∧ SigmaFinite (μ.restrict t)
state_after: case intro.intro.intro.intro.intro
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
inst✝³ : Countable ι
m : MeasurableSpace α
μ : Measure α
inst✝² : TopologicalSpace β
f g✝ : α → β
inst✝¹ : Zero β
inst✝ : T2Space β
g : α → β
hg : FinStronglyMeasurable g μ
hfg : f =ᶠ[ae μ] g
t : Set α
ht : MeasurableSet t
hgt_zero : ∀ x ∈ tᶜ, g x = 0
htμ : SigmaFinite (μ.restrict t)
⊢ f =ᶠ[ae (μ.restrict tᶜ)] 0
tactic: refine ⟨t, ht, ?_, htμ⟩
state_before: case intro.intro.intro.intro.intro
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
inst✝³ : Countable ι
m : MeasurableSpace α
μ : Measure α
inst✝² : TopologicalSpace β
f g✝ : α → β
inst✝¹ : Zero β
inst✝ : T2Space β
g : α → β
hg : FinStronglyMeasurable g μ
hfg : f =ᶠ[ae μ] g
t : Set α
ht : MeasurableSet t
hgt_zero : ∀ x ∈ tᶜ, g x = 0
htμ : SigmaFinite (μ.restrict t)
⊢ f =ᶠ[ae (μ.restrict tᶜ)] 0
state_after: case intro.intro.intro.intro.intro
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
inst✝³ : Countable ι
m : MeasurableSpace α
μ : Measure α
inst✝² : TopologicalSpace β
f g✝ : α → β
inst✝¹ : Zero β
inst✝ : T2Space β
g : α → β
hg : FinStronglyMeasurable g μ
hfg : f =ᶠ[ae μ] g
t : Set α
ht : MeasurableSet t
hgt_zero : ∀ x ∈ tᶜ, g x = 0
htμ : SigmaFinite (μ.restrict t)
⊢ g =ᶠ[ae (μ.restrict tᶜ)] 0
tactic: refine EventuallyEq.trans (ae_restrict_of_ae hfg) ?_
state_before: case intro.intro.intro.intro.intro
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
inst✝³ : Countable ι
m : MeasurableSpace α
μ : Measure α
inst✝² : TopologicalSpace β
f g✝ : α → β
inst✝¹ : Zero β
inst✝ : T2Space β
g : α → β
hg : FinStronglyMeasurable g μ
hfg : f =ᶠ[ae μ] g
t : Set α
ht : MeasurableSet t
hgt_zero : ∀ x ∈ tᶜ, g x = 0
htμ : SigmaFinite (μ.restrict t)
⊢ g =ᶠ[ae (μ.restrict tᶜ)] 0
state_after: case intro.intro.intro.intro.intro
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
inst✝³ : Countable ι
m : MeasurableSpace α
μ : Measure α
inst✝² : TopologicalSpace β
f g✝ : α → β
inst✝¹ : Zero β
inst✝ : T2Space β
g : α → β
hg : FinStronglyMeasurable g μ
hfg : f =ᶠ[ae μ] g
t : Set α
ht : MeasurableSet t
hgt_zero : ∀ x ∈ tᶜ, g x = 0
htμ : SigmaFinite (μ.restrict t)
⊢ ∀ᵐ (x : α) ∂μ, x ∈ tᶜ → g x = 0 x
tactic: rw [EventuallyEq, ae_restrict_iff' ht.compl]
state_before: case intro.intro.intro.intro.intro
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
inst✝³ : Countable ι
m : MeasurableSpace α
μ : Measure α
inst✝² : TopologicalSpace β
f g✝ : α → β
inst✝¹ : Zero β
inst✝ : T2Space β
g : α → β
hg : FinStronglyMeasurable g μ
hfg : f =ᶠ[ae μ] g
t : Set α
ht : MeasurableSet t
hgt_zero : ∀ x ∈ tᶜ, g x = 0
htμ : SigmaFinite (μ.restrict t)
⊢ ∀ᵐ (x : α) ∂μ, x ∈ tᶜ → g x = 0 x
state_after: no goals
tactic: exact eventually_of_forall hgt_zero