Theorem: MeasureTheory.Measure.rnDeriv_smul_left
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✝ ν μ : Measure α
inst✝¹ : IsFiniteMeasure ν
inst✝ : ν.HaveLebesgueDecomposition μ
r : ℝ≥0
⊢ (r • ν).rnDeriv μ =ᶠ[ae μ] r • ν.rnDeriv μ
state_after: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ ν μ : Measure α
inst✝¹ : IsFiniteMeasure ν
inst✝ : ν.HaveLebesgueDecomposition μ
r : ℝ≥0
⊢ μ.withDensity ((r • ν).rnDeriv μ) = μ.withDensity (r • ν.rnDeriv μ)

case hf
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ ν μ : Measure α
inst✝¹ : IsFiniteMeasure ν
inst✝ : ν.HaveLebesgueDecomposition μ
r : ℝ≥0
⊢ AEMeasurable ((r • ν).rnDeriv μ) μ

case hg
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ ν μ : Measure α
inst✝¹ : IsFiniteMeasure ν
inst✝ : ν.HaveLebesgueDecomposition μ
r : ℝ≥0
⊢ AEMeasurable (r • ν.rnDeriv μ) μ

case hfi
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ ν μ : Measure α
inst✝¹ : IsFiniteMeasure ν
inst✝ : ν.HaveLebesgueDecomposition μ
r : ℝ≥0
⊢ ∫⁻ (x : α), (r • ν).rnDeriv μ x ∂μ ≠ ⊤

tactic: simp_rw [ENNReal.smul_def]
state_before: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ ν μ : Measure α
inst✝¹ : IsFiniteMeasure ν
inst✝ : ν.HaveLebesgueDecomposition μ
r : ℝ≥0
⊢ μ.withDensity ((r • ν).rnDeriv μ) = μ.withDensity (r • ν.rnDeriv μ)
state_after: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ ν μ : Measure α
inst✝¹ : IsFiniteMeasure ν
inst✝ : ν.HaveLebesgueDecomposition μ
r : ℝ≥0
⊢ μ.withDensity ((↑r • ν).rnDeriv μ) = μ.withDensity (↑r • ν.rnDeriv μ)

tactic: rw [withDensity_smul _ (measurable_rnDeriv _ _)]
state_before: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ ν μ : Measure α
inst✝¹ : IsFiniteMeasure ν
inst✝ : ν.HaveLebesgueDecomposition μ
r : ℝ≥0
⊢ μ.withDensity ((↑r • ν).rnDeriv μ) = μ.withDensity (↑r • ν.rnDeriv μ)
state_after: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ ν μ : Measure α
inst✝¹ : IsFiniteMeasure ν
inst✝ : ν.HaveLebesgueDecomposition μ
r : ℝ≥0
⊢ μ.withDensity ((↑r • ν).rnDeriv μ) = ↑r • μ.withDensity (ν.rnDeriv μ)

tactic: suffices (r • ν).singularPart μ + withDensity μ (rnDeriv (r • ν) μ)
    = (r • ν).singularPart μ + r • withDensity μ (rnDeriv ν μ) by
  rwa [Measure.add_right_inj] at this
state_before: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ ν μ : Measure α
inst✝¹ : IsFiniteMeasure ν
inst✝ : ν.HaveLebesgueDecomposition μ
r : ℝ≥0
⊢ μ.withDensity ((↑r • ν).rnDeriv μ) = ↑r • μ.withDensity (ν.rnDeriv μ)
state_after: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ ν μ : Measure α
inst✝¹ : IsFiniteMeasure ν
inst✝ : ν.HaveLebesgueDecomposition μ
r : ℝ≥0
⊢ (r • ν).singularPart μ + μ.withDensity ((r • ν).rnDeriv μ) = (r • ν).singularPart μ + r • μ.withDensity (ν.rnDeriv μ)

tactic: rw [← (r • ν).haveLebesgueDecomposition_add μ, singularPart_smul, ← smul_add,
  ← ν.haveLebesgueDecomposition_add μ]
state_before: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ ν μ : Measure α
inst✝¹ : IsFiniteMeasure ν
inst✝ : ν.HaveLebesgueDecomposition μ
r : ℝ≥0
⊢ (r • ν).singularPart μ + μ.withDensity ((r • ν).rnDeriv μ) = (r • ν).singularPart μ + r • μ.withDensity (ν.rnDeriv μ)
state_after: no goals

tactic: rwa [Measure.add_right_inj] at this
state_before: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ ν μ : Measure α
inst✝¹ : IsFiniteMeasure ν
inst✝ : ν.HaveLebesgueDecomposition μ
r : ℝ≥0
this :
  (r • ν).singularPart μ + μ.withDensity ((r • ν).rnDeriv μ) = (r • ν).singularPart μ + r • μ.withDensity (ν.rnDeriv μ)
⊢ μ.withDensity ((↑r • ν).rnDeriv μ) = ↑r • μ.withDensity (ν.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✝ ν μ : Measure α
inst✝¹ : IsFiniteMeasure ν
inst✝ : ν.HaveLebesgueDecomposition μ
r : ℝ≥0
⊢ AEMeasurable ((r • ν).rnDeriv μ) μ
state_after: no goals

tactic: exact (measurable_rnDeriv _ _).aemeasurable.const_smul _
state_before: case hg
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ ν μ : Measure α
inst✝¹ : IsFiniteMeasure ν
inst✝ : ν.HaveLebesgueDecomposition μ
r : ℝ≥0
⊢ AEMeasurable (r • ν.rnDeriv μ) μ
state_after: no goals

tactic: exact (lintegral_rnDeriv_lt_top (r • ν) μ).ne
state_before: case hfi
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ✝ ν✝ ν μ : Measure α
inst✝¹ : IsFiniteMeasure ν
inst✝ : ν.HaveLebesgueDecomposition μ
r : ℝ≥0
⊢ ∫⁻ (x : α), (r • ν).rnDeriv μ x ∂μ ≠ ⊤
state_after: no goals