Theorem: MeasurableEmbedding.rnDeriv_map_aux
File: Mathlib/MeasureTheory/Decomposition/RadonNikodym.lean

Proof steps:
state_before: α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
mβ : MeasurableSpace β
f : α → β
hf : MeasurableEmbedding f
hμν : μ ≪ ν
inst✝¹ : SigmaFinite μ
inst✝ : SigmaFinite ν
⊢ (fun x => (map f μ).rnDeriv (map f ν) (f x)) =ᶠ[ae ν] μ.rnDeriv ν
state_after: case refine_1
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
mβ : MeasurableSpace β
f : α → β
hf : MeasurableEmbedding f
hμν : μ ≪ ν
inst✝¹ : SigmaFinite μ
inst✝ : SigmaFinite ν
⊢ Measurable fun x => (map f μ).rnDeriv (map f ν) (f x)

case refine_2
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
mβ : MeasurableSpace β
f : α → β
hf : MeasurableEmbedding f
hμν : μ ≪ ν
inst✝¹ : SigmaFinite μ
inst✝ : SigmaFinite ν
⊢ Measurable (μ.rnDeriv ν)

case refine_3
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
mβ : MeasurableSpace β
f : α → β
hf : MeasurableEmbedding f
hμν : μ ≪ ν
inst✝¹ : SigmaFinite μ
inst✝ : SigmaFinite ν
s : Set α
x✝¹ : MeasurableSet s
x✝ : ν s < ⊤
⊢ ∫⁻ (x : α) in s, (map f μ).rnDeriv (map f ν) (f x) ∂ν = ∫⁻ (x : α) in s, μ.rnDeriv ν x ∂ν
tactic: refine ae_eq_of_forall_setLIntegral_eq_of_sigmaFinite ?_ ?_ (fun s _ _ ↦ ?_)
state_before: case refine_3
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
mβ : MeasurableSpace β
f : α → β
hf : MeasurableEmbedding f
hμν : μ ≪ ν
inst✝¹ : SigmaFinite μ
inst✝ : SigmaFinite ν
s : Set α
x✝¹ : MeasurableSet s
x✝ : ν s < ⊤
⊢ ∫⁻ (x : α) in s, (map f μ).rnDeriv (map f ν) (f x) ∂ν = ∫⁻ (x : α) in s, μ.rnDeriv ν x ∂ν
state_after: case refine_3
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
mβ : MeasurableSpace β
f : α → β
hf : MeasurableEmbedding f
hμν : μ ≪ ν
inst✝¹ : SigmaFinite μ
inst✝ : SigmaFinite ν
s : Set α
x✝¹ : MeasurableSet s
x✝ : ν s < ⊤
⊢ ∫⁻ (a : β), (map f μ).rnDeriv (map f ν) a ∂map f (ν.restrict s) = μ s
tactic: rw [← hf.lintegral_map, Measure.setLIntegral_rnDeriv hμν]
state_before: case refine_3
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
mβ : MeasurableSpace β
f : α → β
hf : MeasurableEmbedding f
hμν : μ ≪ ν
inst✝¹ : SigmaFinite μ
inst✝ : SigmaFinite ν
s : Set α
x✝¹ : MeasurableSet s
x✝ : ν s < ⊤
⊢ ∫⁻ (a : β), (map f μ).rnDeriv (map f ν) a ∂map f (ν.restrict s) = μ s
state_after: case refine_3
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
mβ : MeasurableSpace β
f : α → β
hf : MeasurableEmbedding f
hμν : μ ≪ ν
inst✝¹ : SigmaFinite μ
inst✝ : SigmaFinite ν
s : Set α
x✝¹ : MeasurableSet s
x✝ : ν s < ⊤
hs_eq : s = f ⁻¹' (f '' s)
⊢ ∫⁻ (a : β), (map f μ).rnDeriv (map f ν) a ∂map f (ν.restrict s) = μ s
tactic: have hs_eq : s = f ⁻¹' (f '' s) := by rw [hf.injective.preimage_image]
state_before: case refine_3
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
mβ : MeasurableSpace β
f : α → β
hf : MeasurableEmbedding f
hμν : μ ≪ ν
inst✝¹ : SigmaFinite μ
inst✝ : SigmaFinite ν
s : Set α
x✝¹ : MeasurableSet s
x✝ : ν s < ⊤
hs_eq : s = f ⁻¹' (f '' s)
⊢ ∫⁻ (a : β), (map f μ).rnDeriv (map f ν) a ∂map f (ν.restrict s) = μ s
state_after: case refine_3
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
mβ : MeasurableSpace β
f : α → β
hf : MeasurableEmbedding f
hμν : μ ≪ ν
inst✝¹ : SigmaFinite μ
inst✝ : SigmaFinite ν
s : Set α
x✝¹ : MeasurableSet s
x✝ : ν s < ⊤
hs_eq : s = f ⁻¹' (f '' s)
this : SigmaFinite (map f ν)
⊢ ∫⁻ (a : β), (map f μ).rnDeriv (map f ν) a ∂map f (ν.restrict s) = μ s
tactic: have : SigmaFinite (ν.map f) := hf.sigmaFinite_map
state_before: case refine_3
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ ν : Measure α
mβ : MeasurableSpace β
f : α → β
hf : MeasurableEmbedding f
hμν : μ ≪ ν
inst✝¹ : SigmaFinite μ
inst✝ : SigmaFinite ν
s : Set α
x✝¹ : MeasurableSet s
x✝ : ν s < ⊤
hs_eq : s = f ⁻¹' (f '' s)
this : SigmaFinite (map f ν)
⊢ ∫⁻ (a : β), (map f μ).rnDeriv (map f ν) a ∂map f (ν.restrict s) = μ s
state_after: no goals
tactic: rw [hs_eq, ← hf.restrict_map, Measure.setLIntegral_rnDeriv (hf.absolutelyContinuous_map hμν),
    hf.map_apply]