Theorem: ContinuousOn.measurable_piecewise
File: Mathlib/MeasureTheory/Constructions/BorelSpace/Basic.lean

Proof steps:
state_before: α : Type u_1
β : Type u_2
γ : Type u_3
γ₂ : Type u_4
δ : Type u_5
ι : Sort y
s✝ t u : Set α
inst✝¹⁵ : TopologicalSpace α
inst✝¹⁴ : MeasurableSpace α
inst✝¹³ : OpensMeasurableSpace α
inst✝¹² : TopologicalSpace β
inst✝¹¹ : MeasurableSpace β
inst✝¹⁰ : OpensMeasurableSpace β
inst✝⁹ : TopologicalSpace γ
inst✝⁸ : MeasurableSpace γ
inst✝⁷ : BorelSpace γ
inst✝⁶ : TopologicalSpace γ₂
inst✝⁵ : MeasurableSpace γ₂
inst✝⁴ : BorelSpace γ₂
inst✝³ : MeasurableSpace δ
α' : Type u_6
inst✝² : TopologicalSpace α'
inst✝¹ : MeasurableSpace α'
f g : α → γ
s : Set α
inst✝ : (j : α) → Decidable (j ∈ s)
hf : ContinuousOn f s
hg : ContinuousOn g sᶜ
hs : MeasurableSet s
⊢ Measurable (s.piecewise f g)
state_after: α : Type u_1
β : Type u_2
γ : Type u_3
γ₂ : Type u_4
δ : Type u_5
ι : Sort y
s✝ t✝ u : Set α
inst✝¹⁵ : TopologicalSpace α
inst✝¹⁴ : MeasurableSpace α
inst✝¹³ : OpensMeasurableSpace α
inst✝¹² : TopologicalSpace β
inst✝¹¹ : MeasurableSpace β
inst✝¹⁰ : OpensMeasurableSpace β
inst✝⁹ : TopologicalSpace γ
inst✝⁸ : MeasurableSpace γ
inst✝⁷ : BorelSpace γ
inst✝⁶ : TopologicalSpace γ₂
inst✝⁵ : MeasurableSpace γ₂
inst✝⁴ : BorelSpace γ₂
inst✝³ : MeasurableSpace δ
α' : Type u_6
inst✝² : TopologicalSpace α'
inst✝¹ : MeasurableSpace α'
f g : α → γ
s : Set α
inst✝ : (j : α) → Decidable (j ∈ s)
hf : ContinuousOn f s
hg : ContinuousOn g sᶜ
hs : MeasurableSet s
t : Set γ
ht : IsOpen t
⊢ MeasurableSet (s.piecewise f g ⁻¹' t)
tactic: refine measurable_of_isOpen fun t ht => ?_
state_before: α : Type u_1
β : Type u_2
γ : Type u_3
γ₂ : Type u_4
δ : Type u_5
ι : Sort y
s✝ t✝ u : Set α
inst✝¹⁵ : TopologicalSpace α
inst✝¹⁴ : MeasurableSpace α
inst✝¹³ : OpensMeasurableSpace α
inst✝¹² : TopologicalSpace β
inst✝¹¹ : MeasurableSpace β
inst✝¹⁰ : OpensMeasurableSpace β
inst✝⁹ : TopologicalSpace γ
inst✝⁸ : MeasurableSpace γ
inst✝⁷ : BorelSpace γ
inst✝⁶ : TopologicalSpace γ₂
inst✝⁵ : MeasurableSpace γ₂
inst✝⁴ : BorelSpace γ₂
inst✝³ : MeasurableSpace δ
α' : Type u_6
inst✝² : TopologicalSpace α'
inst✝¹ : MeasurableSpace α'
f g : α → γ
s : Set α
inst✝ : (j : α) → Decidable (j ∈ s)
hf : ContinuousOn f s
hg : ContinuousOn g sᶜ
hs : MeasurableSet s
t : Set γ
ht : IsOpen t
⊢ MeasurableSet (s.piecewise f g ⁻¹' t)
state_after: α : Type u_1
β : Type u_2
γ : Type u_3
γ₂ : Type u_4
δ : Type u_5
ι : Sort y
s✝ t✝ u : Set α
inst✝¹⁵ : TopologicalSpace α
inst✝¹⁴ : MeasurableSpace α
inst✝¹³ : OpensMeasurableSpace α
inst✝¹² : TopologicalSpace β
inst✝¹¹ : MeasurableSpace β
inst✝¹⁰ : OpensMeasurableSpace β
inst✝⁹ : TopologicalSpace γ
inst✝⁸ : MeasurableSpace γ
inst✝⁷ : BorelSpace γ
inst✝⁶ : TopologicalSpace γ₂
inst✝⁵ : MeasurableSpace γ₂
inst✝⁴ : BorelSpace γ₂
inst✝³ : MeasurableSpace δ
α' : Type u_6
inst✝² : TopologicalSpace α'
inst✝¹ : MeasurableSpace α'
f g : α → γ
s : Set α
inst✝ : (j : α) → Decidable (j ∈ s)
hf : ContinuousOn f s
hg : ContinuousOn g sᶜ
hs : MeasurableSet s
t : Set γ
ht : IsOpen t
⊢ MeasurableSet (f ⁻¹' t ∩ s ∪ g ⁻¹' t \ s)
tactic: rw [piecewise_preimage, Set.ite]
state_before: α : Type u_1
β : Type u_2
γ : Type u_3
γ₂ : Type u_4
δ : Type u_5
ι : Sort y
s✝ t✝ u : Set α
inst✝¹⁵ : TopologicalSpace α
inst✝¹⁴ : MeasurableSpace α
inst✝¹³ : OpensMeasurableSpace α
inst✝¹² : TopologicalSpace β
inst✝¹¹ : MeasurableSpace β
inst✝¹⁰ : OpensMeasurableSpace β
inst✝⁹ : TopologicalSpace γ
inst✝⁸ : MeasurableSpace γ
inst✝⁷ : BorelSpace γ
inst✝⁶ : TopologicalSpace γ₂
inst✝⁵ : MeasurableSpace γ₂
inst✝⁴ : BorelSpace γ₂
inst✝³ : MeasurableSpace δ
α' : Type u_6
inst✝² : TopologicalSpace α'
inst✝¹ : MeasurableSpace α'
f g : α → γ
s : Set α
inst✝ : (j : α) → Decidable (j ∈ s)
hf : ContinuousOn f s
hg : ContinuousOn g sᶜ
hs : MeasurableSet s
t : Set γ
ht : IsOpen t
⊢ MeasurableSet (f ⁻¹' t ∩ s ∪ g ⁻¹' t \ s)
state_after: case h₁
α : Type u_1
β : Type u_2
γ : Type u_3
γ₂ : Type u_4
δ : Type u_5
ι : Sort y
s✝ t✝ u : Set α
inst✝¹⁵ : TopologicalSpace α
inst✝¹⁴ : MeasurableSpace α
inst✝¹³ : OpensMeasurableSpace α
inst✝¹² : TopologicalSpace β
inst✝¹¹ : MeasurableSpace β
inst✝¹⁰ : OpensMeasurableSpace β
inst✝⁹ : TopologicalSpace γ
inst✝⁸ : MeasurableSpace γ
inst✝⁷ : BorelSpace γ
inst✝⁶ : TopologicalSpace γ₂
inst✝⁵ : MeasurableSpace γ₂
inst✝⁴ : BorelSpace γ₂
inst✝³ : MeasurableSpace δ
α' : Type u_6
inst✝² : TopologicalSpace α'
inst✝¹ : MeasurableSpace α'
f g : α → γ
s : Set α
inst✝ : (j : α) → Decidable (j ∈ s)
hf : ContinuousOn f s
hg : ContinuousOn g sᶜ
hs : MeasurableSet s
t : Set γ
ht : IsOpen t
⊢ MeasurableSet (f ⁻¹' t ∩ s)

case h₂
α : Type u_1
β : Type u_2
γ : Type u_3
γ₂ : Type u_4
δ : Type u_5
ι : Sort y
s✝ t✝ u : Set α
inst✝¹⁵ : TopologicalSpace α
inst✝¹⁴ : MeasurableSpace α
inst✝¹³ : OpensMeasurableSpace α
inst✝¹² : TopologicalSpace β
inst✝¹¹ : MeasurableSpace β
inst✝¹⁰ : OpensMeasurableSpace β
inst✝⁹ : TopologicalSpace γ
inst✝⁸ : MeasurableSpace γ
inst✝⁷ : BorelSpace γ
inst✝⁶ : TopologicalSpace γ₂
inst✝⁵ : MeasurableSpace γ₂
inst✝⁴ : BorelSpace γ₂
inst✝³ : MeasurableSpace δ
α' : Type u_6
inst✝² : TopologicalSpace α'
inst✝¹ : MeasurableSpace α'
f g : α → γ
s : Set α
inst✝ : (j : α) → Decidable (j ∈ s)
hf : ContinuousOn f s
hg : ContinuousOn g sᶜ
hs : MeasurableSet s
t : Set γ
ht : IsOpen t
⊢ MeasurableSet (g ⁻¹' t \ s)
tactic: apply MeasurableSet.union