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

tactic: rw [← withDensity_eq_iff]
state_before: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν ν₁ ν₂ μ : Measure α
inst✝⁴ : IsFiniteMeasure ν₁
inst✝³ : IsFiniteMeasure ν₂
inst✝² : ν₁.HaveLebesgueDecomposition μ
inst✝¹ : ν₂.HaveLebesgueDecomposition μ
inst✝ : (ν₁ + ν₂).HaveLebesgueDecomposition μ
⊢ (ν₁ + ν₂).rnDeriv μ =ᶠ[ae μ] ν₁.rnDeriv μ + ν₂.rnDeriv μ
state_after: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν ν₁ ν₂ μ : Measure α
inst✝⁴ : IsFiniteMeasure ν₁
inst✝³ : IsFiniteMeasure ν₂
inst✝² : ν₁.HaveLebesgueDecomposition μ
inst✝¹ : ν₂.HaveLebesgueDecomposition μ
inst✝ : (ν₁ + ν₂).HaveLebesgueDecomposition μ
⊢ μ.withDensity ((ν₁ + ν₂).rnDeriv μ) = μ.withDensity (ν₁.rnDeriv μ + ν₂.rnDeriv μ)

case hf
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν ν₁ ν₂ μ : Measure α
inst✝⁴ : IsFiniteMeasure ν₁
inst✝³ : IsFiniteMeasure ν₂
inst✝² : ν₁.HaveLebesgueDecomposition μ
inst✝¹ : ν₂.HaveLebesgueDecomposition μ
inst✝ : (ν₁ + ν₂).HaveLebesgueDecomposition μ
⊢ AEMeasurable ((ν₁ + ν₂).rnDeriv μ) μ

case hg
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν ν₁ ν₂ μ : Measure α
inst✝⁴ : IsFiniteMeasure ν₁
inst✝³ : IsFiniteMeasure ν₂
inst✝² : ν₁.HaveLebesgueDecomposition μ
inst✝¹ : ν₂.HaveLebesgueDecomposition μ
inst✝ : (ν₁ + ν₂).HaveLebesgueDecomposition μ
⊢ AEMeasurable (ν₁.rnDeriv μ + ν₂.rnDeriv μ) μ

case hfi
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν ν₁ ν₂ μ : Measure α
inst✝⁴ : IsFiniteMeasure ν₁
inst✝³ : IsFiniteMeasure ν₂
inst✝² : ν₁.HaveLebesgueDecomposition μ
inst✝¹ : ν₂.HaveLebesgueDecomposition μ
inst✝ : (ν₁ + ν₂).HaveLebesgueDecomposition μ
⊢ ∫⁻ (x : α), (ν₁ + ν₂).rnDeriv μ x ∂μ ≠ ⊤

tactic: suffices (ν₁ + ν₂).singularPart μ + μ.withDensity ((ν₁ + ν₂).rnDeriv μ)
    = (ν₁ + ν₂).singularPart μ + μ.withDensity (ν₁.rnDeriv μ + ν₂.rnDeriv μ) by
  rwa [add_right_inj] at this
state_before: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν ν₁ ν₂ μ : Measure α
inst✝⁴ : IsFiniteMeasure ν₁
inst✝³ : IsFiniteMeasure ν₂
inst✝² : ν₁.HaveLebesgueDecomposition μ
inst✝¹ : ν₂.HaveLebesgueDecomposition μ
inst✝ : (ν₁ + ν₂).HaveLebesgueDecomposition μ
⊢ μ.withDensity ((ν₁ + ν₂).rnDeriv μ) = μ.withDensity (ν₁.rnDeriv μ + ν₂.rnDeriv μ)
state_after: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν ν₁ ν₂ μ : Measure α
inst✝⁴ : IsFiniteMeasure ν₁
inst✝³ : IsFiniteMeasure ν₂
inst✝² : ν₁.HaveLebesgueDecomposition μ
inst✝¹ : ν₂.HaveLebesgueDecomposition μ
inst✝ : (ν₁ + ν₂).HaveLebesgueDecomposition μ
⊢ (ν₁ + ν₂).singularPart μ + μ.withDensity ((ν₁ + ν₂).rnDeriv μ) =
    (ν₁ + ν₂).singularPart μ + μ.withDensity (ν₁.rnDeriv μ + ν₂.rnDeriv μ)

tactic: rw [← (ν₁ + ν₂).haveLebesgueDecomposition_add μ, singularPart_add,
  withDensity_add_left (measurable_rnDeriv _ _), add_assoc,
  add_comm (ν₂.singularPart μ), add_assoc, add_comm _ (ν₂.singularPart μ),
  ← ν₂.haveLebesgueDecomposition_add μ, ← add_assoc, ← ν₁.haveLebesgueDecomposition_add μ]
state_before: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν ν₁ ν₂ μ : Measure α
inst✝⁴ : IsFiniteMeasure ν₁
inst✝³ : IsFiniteMeasure ν₂
inst✝² : ν₁.HaveLebesgueDecomposition μ
inst✝¹ : ν₂.HaveLebesgueDecomposition μ
inst✝ : (ν₁ + ν₂).HaveLebesgueDecomposition μ
⊢ (ν₁ + ν₂).singularPart μ + μ.withDensity ((ν₁ + ν₂).rnDeriv μ) =
    (ν₁ + ν₂).singularPart μ + μ.withDensity (ν₁.rnDeriv μ + ν₂.rnDeriv μ)
state_after: no goals

tactic: rwa [add_right_inj] at this
state_before: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν ν₁ ν₂ μ : Measure α
inst✝⁴ : IsFiniteMeasure ν₁
inst✝³ : IsFiniteMeasure ν₂
inst✝² : ν₁.HaveLebesgueDecomposition μ
inst✝¹ : ν₂.HaveLebesgueDecomposition μ
inst✝ : (ν₁ + ν₂).HaveLebesgueDecomposition μ
this :
  (ν₁ + ν₂).singularPart μ + μ.withDensity ((ν₁ + ν₂).rnDeriv μ) =
    (ν₁ + ν₂).singularPart μ + μ.withDensity (ν₁.rnDeriv μ + ν₂.rnDeriv μ)
⊢ μ.withDensity ((ν₁ + ν₂).rnDeriv μ) = μ.withDensity (ν₁.rnDeriv μ + ν₂.rnDeriv μ)
state_after: no goals

tactic: exact (measurable_rnDeriv _ _).aemeasurable
state_before: case hf
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν ν₁ ν₂ μ : Measure α
inst✝⁴ : IsFiniteMeasure ν₁
inst✝³ : IsFiniteMeasure ν₂
inst✝² : ν₁.HaveLebesgueDecomposition μ
inst✝¹ : ν₂.HaveLebesgueDecomposition μ
inst✝ : (ν₁ + ν₂).HaveLebesgueDecomposition μ
⊢ AEMeasurable ((ν₁ + ν₂).rnDeriv μ) μ
state_after: no goals

tactic: exact ((measurable_rnDeriv _ _).add (measurable_rnDeriv _ _)).aemeasurable
state_before: case hg
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν ν₁ ν₂ μ : Measure α
inst✝⁴ : IsFiniteMeasure ν₁
inst✝³ : IsFiniteMeasure ν₂
inst✝² : ν₁.HaveLebesgueDecomposition μ
inst✝¹ : ν₂.HaveLebesgueDecomposition μ
inst✝ : (ν₁ + ν₂).HaveLebesgueDecomposition μ
⊢ AEMeasurable (ν₁.rnDeriv μ + ν₂.rnDeriv μ) μ
state_after: no goals

tactic: exact (lintegral_rnDeriv_lt_top (ν₁ + ν₂) μ).ne
state_before: case hfi
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν ν₁ ν₂ μ : Measure α
inst✝⁴ : IsFiniteMeasure ν₁
inst✝³ : IsFiniteMeasure ν₂
inst✝² : ν₁.HaveLebesgueDecomposition μ
inst✝¹ : ν₂.HaveLebesgueDecomposition μ
inst✝ : (ν₁ + ν₂).HaveLebesgueDecomposition μ
⊢ ∫⁻ (x : α), (ν₁ + ν₂).rnDeriv μ x ∂μ ≠ ⊤
state_after: no goals