Theorem: MeasureTheory.Measure.absolutelyContinuous_withDensity_rnDeriv
File: Mathlib/MeasureTheory/Decomposition/Lebesgue.lean

Proof steps:
state_before: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
inst✝ : ν.HaveLebesgueDecomposition μ
hμν : μ ≪ ν
⊢ μ ≪ μ.withDensity (ν.rnDeriv μ)
state_after: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
inst✝ : ν.HaveLebesgueDecomposition μ
hμν : μ ≪ ν.singularPart μ + μ.withDensity (ν.rnDeriv μ)
⊢ μ ≪ μ.withDensity (ν.rnDeriv μ)
tactic: rw [haveLebesgueDecomposition_add ν μ] at hμν
state_before: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
inst✝ : ν.HaveLebesgueDecomposition μ
hμν : μ ≪ ν.singularPart μ + μ.withDensity (ν.rnDeriv μ)
⊢ μ ≪ μ.withDensity (ν.rnDeriv μ)
state_after: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
inst✝ : ν.HaveLebesgueDecomposition μ
hμν : μ ≪ ν.singularPart μ + μ.withDensity (ν.rnDeriv μ)
s : Set α
x✝ : MeasurableSet s
hνs : (μ.withDensity (ν.rnDeriv μ)) s = 0
⊢ μ s = 0
tactic: refine AbsolutelyContinuous.mk (fun s _ hνs ↦ ?_)
state_before: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
inst✝ : ν.HaveLebesgueDecomposition μ
hμν : μ ≪ ν.singularPart μ + μ.withDensity (ν.rnDeriv μ)
s : Set α
x✝ : MeasurableSet s
hνs : (μ.withDensity (ν.rnDeriv μ)) s = 0
⊢ μ s = 0
state_after: case intro.intro.intro
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
inst✝ : ν.HaveLebesgueDecomposition μ
hμν : μ ≪ ν.singularPart μ + μ.withDensity (ν.rnDeriv μ)
s : Set α
x✝ : MeasurableSet s
hνs : (μ.withDensity (ν.rnDeriv μ)) s = 0
t : Set α
left✝ : MeasurableSet t
ht1 : (ν.singularPart μ) t = 0
ht2 : μ tᶜ = 0
⊢ μ s = 0
tactic: obtain ⟨t, _, ht1, ht2⟩ := mutuallySingular_singularPart ν μ
state_before: case intro.intro.intro
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
inst✝ : ν.HaveLebesgueDecomposition μ
hμν : μ ≪ ν.singularPart μ + μ.withDensity (ν.rnDeriv μ)
s : Set α
x✝ : MeasurableSet s
hνs : (μ.withDensity (ν.rnDeriv μ)) s = 0
t : Set α
left✝ : MeasurableSet t
ht1 : (ν.singularPart μ) t = 0
ht2 : μ tᶜ = 0
⊢ μ s = 0
state_after: case intro.intro.intro
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
inst✝ : ν.HaveLebesgueDecomposition μ
hμν : μ ≪ ν.singularPart μ + μ.withDensity (ν.rnDeriv μ)
s : Set α
x✝ : MeasurableSet s
hνs : (μ.withDensity (ν.rnDeriv μ)) s = 0
t : Set α
left✝ : MeasurableSet t
ht1 : (ν.singularPart μ) t = 0
ht2 : μ tᶜ = 0
⊢ μ (s ∩ ?intro.intro.intro ∪ s ∩ ?intro.intro.introᶜ) = 0

case intro.intro.intro
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
inst✝ : ν.HaveLebesgueDecomposition μ
hμν : μ ≪ ν.singularPart μ + μ.withDensity (ν.rnDeriv μ)
s : Set α
x✝ : MeasurableSet s
hνs : (μ.withDensity (ν.rnDeriv μ)) s = 0
t : Set α
left✝ : MeasurableSet t
ht1 : (ν.singularPart μ) t = 0
ht2 : μ tᶜ = 0
⊢ Set α
tactic: rw [← inter_union_compl s]
state_before: case intro.intro.intro
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
inst✝ : ν.HaveLebesgueDecomposition μ
hμν : μ ≪ ν.singularPart μ + μ.withDensity (ν.rnDeriv μ)
s : Set α
x✝ : MeasurableSet s
hνs : (μ.withDensity (ν.rnDeriv μ)) s = 0
t : Set α
left✝ : MeasurableSet t
ht1 : (ν.singularPart μ) t = 0
ht2 : μ tᶜ = 0
⊢ μ (s ∩ ?intro.intro.intro ∪ s ∩ ?intro.intro.introᶜ) = 0

case intro.intro.intro
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
inst✝ : ν.HaveLebesgueDecomposition μ
hμν : μ ≪ ν.singularPart μ + μ.withDensity (ν.rnDeriv μ)
s : Set α
x✝ : MeasurableSet s
hνs : (μ.withDensity (ν.rnDeriv μ)) s = 0
t : Set α
left✝ : MeasurableSet t
ht1 : (ν.singularPart μ) t = 0
ht2 : μ tᶜ = 0
⊢ Set α
state_after: case intro.intro.intro
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
inst✝ : ν.HaveLebesgueDecomposition μ
hμν : μ ≪ ν.singularPart μ + μ.withDensity (ν.rnDeriv μ)
s : Set α
x✝ : MeasurableSet s
hνs : (μ.withDensity (ν.rnDeriv μ)) s = 0
t : Set α
left✝ : MeasurableSet t
ht1 : (ν.singularPart μ) t = 0
ht2 : μ tᶜ = 0
⊢ μ (s ∩ t) + μ (s ∩ tᶜ) ≤ 0
tactic: refine le_antisymm ((measure_union_le (s ∩ t) (s ∩ tᶜ)).trans ?_) (zero_le _)
state_before: case intro.intro.intro
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
inst✝ : ν.HaveLebesgueDecomposition μ
hμν : μ ≪ ν.singularPart μ + μ.withDensity (ν.rnDeriv μ)
s : Set α
x✝ : MeasurableSet s
hνs : (μ.withDensity (ν.rnDeriv μ)) s = 0
t : Set α
left✝ : MeasurableSet t
ht1 : (ν.singularPart μ) t = 0
ht2 : μ tᶜ = 0
⊢ μ (s ∩ t) + μ (s ∩ tᶜ) ≤ 0
state_after: case intro.intro.intro
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
inst✝ : ν.HaveLebesgueDecomposition μ
hμν : μ ≪ ν.singularPart μ + μ.withDensity (ν.rnDeriv μ)
s : Set α
x✝ : MeasurableSet s
hνs : (μ.withDensity (ν.rnDeriv μ)) s = 0
t : Set α
left✝ : MeasurableSet t
ht1 : (ν.singularPart μ) t = 0
ht2 : μ tᶜ = 0
⊢ μ (s ∩ t) = 0 ∧ μ (s ∩ tᶜ) = 0
tactic: simp only [nonpos_iff_eq_zero, add_eq_zero]
state_before: case intro.intro.intro
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
inst✝ : ν.HaveLebesgueDecomposition μ
hμν : μ ≪ ν.singularPart μ + μ.withDensity (ν.rnDeriv μ)
s : Set α
x✝ : MeasurableSet s
hνs : (μ.withDensity (ν.rnDeriv μ)) s = 0
t : Set α
left✝ : MeasurableSet t
ht1 : (ν.singularPart μ) t = 0
ht2 : μ tᶜ = 0
⊢ μ (s ∩ t) = 0 ∧ μ (s ∩ tᶜ) = 0
state_after: case intro.intro.intro.left
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
inst✝ : ν.HaveLebesgueDecomposition μ
hμν : μ ≪ ν.singularPart μ + μ.withDensity (ν.rnDeriv μ)
s : Set α
x✝ : MeasurableSet s
hνs : (μ.withDensity (ν.rnDeriv μ)) s = 0
t : Set α
left✝ : MeasurableSet t
ht1 : (ν.singularPart μ) t = 0
ht2 : μ tᶜ = 0
⊢ μ (s ∩ t) = 0

case intro.intro.intro.right
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
inst✝ : ν.HaveLebesgueDecomposition μ
hμν : μ ≪ ν.singularPart μ + μ.withDensity (ν.rnDeriv μ)
s : Set α
x✝ : MeasurableSet s
hνs : (μ.withDensity (ν.rnDeriv μ)) s = 0
t : Set α
left✝ : MeasurableSet t
ht1 : (ν.singularPart μ) t = 0
ht2 : μ tᶜ = 0
⊢ μ (s ∩ tᶜ) = 0
tactic: constructor