Theorem: MeasureTheory.IsLocallyFiniteMeasure.withDensity_coe
File: Mathlib/MeasureTheory/Measure/WithDensity.lean

Proof steps:
state_before: α : Type u_1
m0 : MeasurableSpace α
μ : Measure α
inst✝² : TopologicalSpace α
inst✝¹ : OpensMeasurableSpace α
inst✝ : IsLocallyFiniteMeasure μ
f : α → ℝ≥0
hf : Continuous f
⊢ IsLocallyFiniteMeasure (μ.withDensity fun x => ↑(f x))
state_after: α : Type u_1
m0 : MeasurableSpace α
μ : Measure α
inst✝² : TopologicalSpace α
inst✝¹ : OpensMeasurableSpace α
inst✝ : IsLocallyFiniteMeasure μ
f : α → ℝ≥0
hf : Continuous f
x : α
⊢ (μ.withDensity fun x => ↑(f x)).FiniteAtFilter (nhds x)
tactic: refine ⟨fun x ↦ ?_⟩
state_before: α : Type u_1
m0 : MeasurableSpace α
μ : Measure α
inst✝² : TopologicalSpace α
inst✝¹ : OpensMeasurableSpace α
inst✝ : IsLocallyFiniteMeasure μ
f : α → ℝ≥0
hf : Continuous f
x : α
⊢ (μ.withDensity fun x => ↑(f x)).FiniteAtFilter (nhds x)
state_after: case intro.intro.intro.intro
α : Type u_1
m0 : MeasurableSpace α
μ : Measure α
inst✝² : TopologicalSpace α
inst✝¹ : OpensMeasurableSpace α
inst✝ : IsLocallyFiniteMeasure μ
f : α → ℝ≥0
hf : Continuous f
x : α
U : Set α
hμU : μ U < ⊤
hUf : U ⊆ {x_1 | (fun a => f a ≤ f x + 1) x_1}
hUx : U ∈ nhds x
hUo : IsOpen U
⊢ (μ.withDensity fun x => ↑(f x)).FiniteAtFilter (nhds x)
tactic: rcases (μ.finiteAt_nhds x).exists_mem_basis ((nhds_basis_opens' x).restrict_subset
    (eventually_le_of_tendsto_lt (lt_add_one _) (hf.tendsto x))) with ⟨U, ⟨⟨hUx, hUo⟩, hUf⟩, hμU⟩
state_before: case intro.intro.intro.intro
α : Type u_1
m0 : MeasurableSpace α
μ : Measure α
inst✝² : TopologicalSpace α
inst✝¹ : OpensMeasurableSpace α
inst✝ : IsLocallyFiniteMeasure μ
f : α → ℝ≥0
hf : Continuous f
x : α
U : Set α
hμU : μ U < ⊤
hUf : U ⊆ {x_1 | (fun a => f a ≤ f x + 1) x_1}
hUx : U ∈ nhds x
hUo : IsOpen U
⊢ (μ.withDensity fun x => ↑(f x)).FiniteAtFilter (nhds x)
state_after: case intro.intro.intro.intro
α : Type u_1
m0 : MeasurableSpace α
μ : Measure α
inst✝² : TopologicalSpace α
inst✝¹ : OpensMeasurableSpace α
inst✝ : IsLocallyFiniteMeasure μ
f : α → ℝ≥0
hf : Continuous f
x : α
U : Set α
hμU : μ U < ⊤
hUf : U ⊆ {x_1 | (fun a => f a ≤ f x + 1) x_1}
hUx : U ∈ nhds x
hUo : IsOpen U
⊢ (μ.withDensity fun x => ↑(f x)) U < ⊤
tactic: refine ⟨U, hUx, ?_⟩
state_before: case intro.intro.intro.intro
α : Type u_1
m0 : MeasurableSpace α
μ : Measure α
inst✝² : TopologicalSpace α
inst✝¹ : OpensMeasurableSpace α
inst✝ : IsLocallyFiniteMeasure μ
f : α → ℝ≥0
hf : Continuous f
x : α
U : Set α
hμU : μ U < ⊤
hUf : U ⊆ {x_1 | (fun a => f a ≤ f x + 1) x_1}
hUx : U ∈ nhds x
hUo : IsOpen U
⊢ (μ.withDensity fun x => ↑(f x)) U < ⊤
state_after: case intro.intro.intro.intro
α : Type u_1
m0 : MeasurableSpace α
μ : Measure α
inst✝² : TopologicalSpace α
inst✝¹ : OpensMeasurableSpace α
inst✝ : IsLocallyFiniteMeasure μ
f : α → ℝ≥0
hf : Continuous f
x : α
U : Set α
hμU : μ U < ⊤
hUf : U ⊆ {x_1 | (fun a => f a ≤ f x + 1) x_1}
hUx : U ∈ nhds x
hUo : IsOpen U
⊢ ∫⁻ (a : α) in U, ↑(f a) ∂μ < ⊤
tactic: rw [withDensity_apply _ hUo.measurableSet]
state_before: case intro.intro.intro.intro
α : Type u_1
m0 : MeasurableSpace α
μ : Measure α
inst✝² : TopologicalSpace α
inst✝¹ : OpensMeasurableSpace α
inst✝ : IsLocallyFiniteMeasure μ
f : α → ℝ≥0
hf : Continuous f
x : α
U : Set α
hμU : μ U < ⊤
hUf : U ⊆ {x_1 | (fun a => f a ≤ f x + 1) x_1}
hUx : U ∈ nhds x
hUo : IsOpen U
⊢ ∫⁻ (a : α) in U, ↑(f a) ∂μ < ⊤
state_after: no goals
tactic: exact setLIntegral_lt_top_of_bddAbove hμU.ne ⟨f x + 1, forall_mem_image.2 hUf⟩