Theorem: ContinuousOn.measurableEmbedding
File: Mathlib/MeasureTheory/Constructions/Polish/Basic.lean

Proof steps:
state_before: α✝ : Type u_1
ι : Type u_2
γ : Type u_3
α : Type u_4
β : Type u_5
tβ : TopologicalSpace β
inst✝⁷ : T2Space β
inst✝⁶ : MeasurableSpace β
inst✝⁵ : MeasurableSpace α
s : Set γ
f : γ → β
inst✝⁴ : BorelSpace β
inst✝³ : TopologicalSpace γ
inst✝² : PolishSpace γ
inst✝¹ : MeasurableSpace γ
inst✝ : BorelSpace γ
hs : MeasurableSet s
f_cont : ContinuousOn f s
f_inj : InjOn f s
⊢ ∀ ⦃s_1 : Set ↑s⦄, MeasurableSet s_1 → MeasurableSet (s.restrict f '' s_1)
state_after: α✝ : Type u_1
ι : Type u_2
γ : Type u_3
α : Type u_4
β : Type u_5
tβ : TopologicalSpace β
inst✝⁷ : T2Space β
inst✝⁶ : MeasurableSpace β
inst✝⁵ : MeasurableSpace α
s : Set γ
f : γ → β
inst✝⁴ : BorelSpace β
inst✝³ : TopologicalSpace γ
inst✝² : PolishSpace γ
inst✝¹ : MeasurableSpace γ
inst✝ : BorelSpace γ
hs : MeasurableSet s
f_cont : ContinuousOn f s
f_inj : InjOn f s
u : Set ↑s
hu : MeasurableSet u
⊢ MeasurableSet (s.restrict f '' u)
tactic: intro u hu
state_before: α✝ : Type u_1
ι : Type u_2
γ : Type u_3
α : Type u_4
β : Type u_5
tβ : TopologicalSpace β
inst✝⁷ : T2Space β
inst✝⁶ : MeasurableSpace β
inst✝⁵ : MeasurableSpace α
s : Set γ
f : γ → β
inst✝⁴ : BorelSpace β
inst✝³ : TopologicalSpace γ
inst✝² : PolishSpace γ
inst✝¹ : MeasurableSpace γ
inst✝ : BorelSpace γ
hs : MeasurableSet s
f_cont : ContinuousOn f s
f_inj : InjOn f s
u : Set ↑s
hu : MeasurableSet u
⊢ MeasurableSet (s.restrict f '' u)
state_after: α✝ : Type u_1
ι : Type u_2
γ : Type u_3
α : Type u_4
β : Type u_5
tβ : TopologicalSpace β
inst✝⁷ : T2Space β
inst✝⁶ : MeasurableSpace β
inst✝⁵ : MeasurableSpace α
s : Set γ
f : γ → β
inst✝⁴ : BorelSpace β
inst✝³ : TopologicalSpace γ
inst✝² : PolishSpace γ
inst✝¹ : MeasurableSpace γ
inst✝ : BorelSpace γ
hs : MeasurableSet s
f_cont : ContinuousOn f s
f_inj : InjOn f s
u : Set ↑s
hu : MeasurableSet u
A : MeasurableSet (Subtype.val '' u)
⊢ MeasurableSet (s.restrict f '' u)
tactic: have A : MeasurableSet (((↑) : s → γ) '' u) :=
        (MeasurableEmbedding.subtype_coe hs).measurableSet_image.2 hu
state_before: α✝ : Type u_1
ι : Type u_2
γ : Type u_3
α : Type u_4
β : Type u_5
tβ : TopologicalSpace β
inst✝⁷ : T2Space β
inst✝⁶ : MeasurableSpace β
inst✝⁵ : MeasurableSpace α
s : Set γ
f : γ → β
inst✝⁴ : BorelSpace β
inst✝³ : TopologicalSpace γ
inst✝² : PolishSpace γ
inst✝¹ : MeasurableSpace γ
inst✝ : BorelSpace γ
hs : MeasurableSet s
f_cont : ContinuousOn f s
f_inj : InjOn f s
u : Set ↑s
hu : MeasurableSet u
A : MeasurableSet (Subtype.val '' u)
⊢ MeasurableSet (s.restrict f '' u)
state_after: α✝ : Type u_1
ι : Type u_2
γ : Type u_3
α : Type u_4
β : Type u_5
tβ : TopologicalSpace β
inst✝⁷ : T2Space β
inst✝⁶ : MeasurableSpace β
inst✝⁵ : MeasurableSpace α
s : Set γ
f : γ → β
inst✝⁴ : BorelSpace β
inst✝³ : TopologicalSpace γ
inst✝² : PolishSpace γ
inst✝¹ : MeasurableSpace γ
inst✝ : BorelSpace γ
hs : MeasurableSet s
f_cont : ContinuousOn f s
f_inj : InjOn f s
u : Set ↑s
hu : MeasurableSet u
A : MeasurableSet (Subtype.val '' u)
B : MeasurableSet (f '' (Subtype.val '' u))
⊢ MeasurableSet (s.restrict f '' u)
tactic: have B : MeasurableSet (f '' (((↑) : s → γ) '' u)) :=
        A.image_of_continuousOn_injOn (f_cont.mono (Subtype.coe_image_subset s u))
          (f_inj.mono (Subtype.coe_image_subset s u))
state_before: α✝ : Type u_1
ι : Type u_2
γ : Type u_3
α : Type u_4
β : Type u_5
tβ : TopologicalSpace β
inst✝⁷ : T2Space β
inst✝⁶ : MeasurableSpace β
inst✝⁵ : MeasurableSpace α
s : Set γ
f : γ → β
inst✝⁴ : BorelSpace β
inst✝³ : TopologicalSpace γ
inst✝² : PolishSpace γ
inst✝¹ : MeasurableSpace γ
inst✝ : BorelSpace γ
hs : MeasurableSet s
f_cont : ContinuousOn f s
f_inj : InjOn f s
u : Set ↑s
hu : MeasurableSet u
A : MeasurableSet (Subtype.val '' u)
B : MeasurableSet (f '' (Subtype.val '' u))
⊢ MeasurableSet (s.restrict f '' u)
state_after: no goals
tactic: rwa [← image_comp] at B