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

tactic: have h_dec := haveLebesgueDecomposition_add μ ν
state_before: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ μ ν : Measure α
inst✝ : μ.HaveLebesgueDecomposition ν
⊢ ν.withDensity (μ.rnDeriv ν) = 0 ↔ μ ⟂ₘ ν
state_after: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ μ ν : Measure α
inst✝ : μ.HaveLebesgueDecomposition ν
h_dec : μ = μ.singularPart ν + ν.withDensity (μ.rnDeriv ν)
⊢ ν.withDensity (μ.rnDeriv ν) = 0 ↔ μ ⟂ₘ ν

tactic: refine ⟨fun h ↦ ?_, fun h ↦ ?_⟩
state_before: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ μ ν : Measure α
inst✝ : μ.HaveLebesgueDecomposition ν
h_dec : μ = μ.singularPart ν + ν.withDensity (μ.rnDeriv ν)
⊢ ν.withDensity (μ.rnDeriv ν) = 0 ↔ μ ⟂ₘ ν
state_after: case refine_1
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ μ ν : Measure α
inst✝ : μ.HaveLebesgueDecomposition ν
h_dec : μ = μ.singularPart ν + ν.withDensity (μ.rnDeriv ν)
h : ν.withDensity (μ.rnDeriv ν) = 0
⊢ μ ⟂ₘ ν

case refine_2
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ μ ν : Measure α
inst✝ : μ.HaveLebesgueDecomposition ν
h_dec : μ = μ.singularPart ν + ν.withDensity (μ.rnDeriv ν)
h : μ ⟂ₘ ν
⊢ ν.withDensity (μ.rnDeriv ν) = 0

tactic: rw [h, add_zero] at h_dec
state_before: case refine_1
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ μ ν : Measure α
inst✝ : μ.HaveLebesgueDecomposition ν
h_dec : μ = μ.singularPart ν + ν.withDensity (μ.rnDeriv ν)
h : ν.withDensity (μ.rnDeriv ν) = 0
⊢ μ ⟂ₘ ν
state_after: case refine_1
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ μ ν : Measure α
inst✝ : μ.HaveLebesgueDecomposition ν
h_dec : μ = μ.singularPart ν
h : ν.withDensity (μ.rnDeriv ν) = 0
⊢ μ ⟂ₘ ν

tactic: rw [h_dec]
state_before: case refine_1
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ μ ν : Measure α
inst✝ : μ.HaveLebesgueDecomposition ν
h_dec : μ = μ.singularPart ν
h : ν.withDensity (μ.rnDeriv ν) = 0
⊢ μ ⟂ₘ ν
state_after: case refine_1
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ μ ν : Measure α
inst✝ : μ.HaveLebesgueDecomposition ν
h_dec : μ = μ.singularPart ν
h : ν.withDensity (μ.rnDeriv ν) = 0
⊢ μ.singularPart ν ⟂ₘ ν

tactic: exact mutuallySingular_singularPart μ ν
state_before: case refine_1
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ μ ν : Measure α
inst✝ : μ.HaveLebesgueDecomposition ν
h_dec : μ = μ.singularPart ν
h : ν.withDensity (μ.rnDeriv ν) = 0
⊢ μ.singularPart ν ⟂ₘ ν
state_after: no goals

tactic: rw [← MutuallySingular.self_iff]
state_before: case refine_2
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ μ ν : Measure α
inst✝ : μ.HaveLebesgueDecomposition ν
h_dec : μ = μ.singularPart ν + ν.withDensity (μ.rnDeriv ν)
h : μ ⟂ₘ ν
⊢ ν.withDensity (μ.rnDeriv ν) = 0
state_after: case refine_2
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ μ ν : Measure α
inst✝ : μ.HaveLebesgueDecomposition ν
h_dec : μ = μ.singularPart ν + ν.withDensity (μ.rnDeriv ν)
h : μ ⟂ₘ ν
⊢ ν.withDensity (μ.rnDeriv ν) ⟂ₘ ν.withDensity (μ.rnDeriv ν)

tactic: rw [h_dec, MutuallySingular.add_left_iff] at h
state_before: case refine_2
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ μ ν : Measure α
inst✝ : μ.HaveLebesgueDecomposition ν
h_dec : μ = μ.singularPart ν + ν.withDensity (μ.rnDeriv ν)
h : μ ⟂ₘ ν
⊢ ν.withDensity (μ.rnDeriv ν) ⟂ₘ ν.withDensity (μ.rnDeriv ν)
state_after: case refine_2
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ μ ν : Measure α
inst✝ : μ.HaveLebesgueDecomposition ν
h_dec : μ = μ.singularPart ν + ν.withDensity (μ.rnDeriv ν)
h : μ.singularPart ν ⟂ₘ ν ∧ ν.withDensity (μ.rnDeriv ν) ⟂ₘ ν
⊢ ν.withDensity (μ.rnDeriv ν) ⟂ₘ ν.withDensity (μ.rnDeriv ν)

tactic: refine MutuallySingular.mono_ac h.2 AbsolutelyContinuous.rfl ?_
state_before: case refine_2
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ μ ν : Measure α
inst✝ : μ.HaveLebesgueDecomposition ν
h_dec : μ = μ.singularPart ν + ν.withDensity (μ.rnDeriv ν)
h : μ.singularPart ν ⟂ₘ ν ∧ ν.withDensity (μ.rnDeriv ν) ⟂ₘ ν
⊢ ν.withDensity (μ.rnDeriv ν) ⟂ₘ ν.withDensity (μ.rnDeriv ν)
state_after: case refine_2
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ μ ν : Measure α
inst✝ : μ.HaveLebesgueDecomposition ν
h_dec : μ = μ.singularPart ν + ν.withDensity (μ.rnDeriv ν)
h : μ.singularPart ν ⟂ₘ ν ∧ ν.withDensity (μ.rnDeriv ν) ⟂ₘ ν
⊢ ν.withDensity (μ.rnDeriv ν) ≪ ν

tactic: exact withDensity_absolutelyContinuous _ _
state_before: case refine_2
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ μ ν : Measure α
inst✝ : μ.HaveLebesgueDecomposition ν
h_dec : μ = μ.singularPart ν + ν.withDensity (μ.rnDeriv ν)
h : μ.singularPart ν ⟂ₘ ν ∧ ν.withDensity (μ.rnDeriv ν) ⟂ₘ ν
⊢ ν.withDensity (μ.rnDeriv ν) ≪ ν
state_after: no goals