Theorem: borel_eq_generateFrom_of_subbasis
File: Mathlib/MeasureTheory/Constructions/BorelSpace/Basic.lean

tactic: induction hu with
| basic u hu => exact GenerateMeasurable.basic u hu
| univ => exact @MeasurableSet.univ α (generateFrom s)
| inter s₁ s₂ _ _ hs₁ hs₂ => exact @MeasurableSet.inter α (generateFrom s) _ _ hs₁ hs₂
| sUnion f hf ih =>
  rcases isOpen_sUnion_countable f (by rwa [hs]) with ⟨v, hv, vf, vu⟩
  rw [← vu]
  exact @MeasurableSet.sUnion α (generateFrom s) _ hv fun x xv => ih _ (vf xv)
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
s : Set (Set α)
t : TopologicalSpace α
inst✝ : SecondCountableTopology α
hs : t = TopologicalSpace.generateFrom s
u : Set α
hu : TopologicalSpace.IsOpen u
⊢ MeasurableSet u
state_after: no goals

tactic: exact GenerateMeasurable.basic u hu
state_before: case basic
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✝¹ : Set α
s : Set (Set α)
t : TopologicalSpace α
inst✝ : SecondCountableTopology α
hs : t = TopologicalSpace.generateFrom s
u✝ u : Set α
hu : u ∈ s
⊢ MeasurableSet u
state_after: no goals

tactic: exact @MeasurableSet.univ α (generateFrom s)
state_before: case univ
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
s : Set (Set α)
t : TopologicalSpace α
inst✝ : SecondCountableTopology α
hs : t = TopologicalSpace.generateFrom s
u : Set α
⊢ MeasurableSet univ
state_after: no goals

tactic: exact @MeasurableSet.inter α (generateFrom s) _ _ hs₁ hs₂
state_before: case inter
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
s : Set (Set α)
t : TopologicalSpace α
inst✝ : SecondCountableTopology α
hs : t = TopologicalSpace.generateFrom s
u s₁ s₂ : Set α
a✝¹ : GenerateOpen s s₁
a✝ : GenerateOpen s s₂
hs₁ : MeasurableSet s₁
hs₂ : MeasurableSet s₂
⊢ MeasurableSet (s₁ ∩ s₂)
state_after: no goals

tactic: rcases isOpen_sUnion_countable f (by rwa [hs]) with ⟨v, hv, vf, vu⟩
state_before: case sUnion
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
s : Set (Set α)
t : TopologicalSpace α
inst✝ : SecondCountableTopology α
hs : t = TopologicalSpace.generateFrom s
u : Set α
f : Set (Set α)
hf : ∀ s_1 ∈ f, GenerateOpen s s_1
ih : ∀ s_1 ∈ f, MeasurableSet s_1
⊢ MeasurableSet (⋃₀ f)
state_after: case sUnion.intro.intro.intro
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
s : Set (Set α)
t : TopologicalSpace α
inst✝ : SecondCountableTopology α
hs : t = TopologicalSpace.generateFrom s
u : Set α
f : Set (Set α)
hf : ∀ s_1 ∈ f, GenerateOpen s s_1
ih : ∀ s_1 ∈ f, MeasurableSet s_1
v : Set (Set α)
hv : v.Countable
vf : v ⊆ f
vu : ⋃₀ v = ⋃₀ f
⊢ MeasurableSet (⋃₀ f)

tactic: rw [← vu]
state_before: case sUnion.intro.intro.intro
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
s : Set (Set α)
t : TopologicalSpace α
inst✝ : SecondCountableTopology α
hs : t = TopologicalSpace.generateFrom s
u : Set α
f : Set (Set α)
hf : ∀ s_1 ∈ f, GenerateOpen s s_1
ih : ∀ s_1 ∈ f, MeasurableSet s_1
v : Set (Set α)
hv : v.Countable
vf : v ⊆ f
vu : ⋃₀ v = ⋃₀ f
⊢ MeasurableSet (⋃₀ f)
state_after: case sUnion.intro.intro.intro
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
s : Set (Set α)
t : TopologicalSpace α
inst✝ : SecondCountableTopology α
hs : t = TopologicalSpace.generateFrom s
u : Set α
f : Set (Set α)
hf : ∀ s_1 ∈ f, GenerateOpen s s_1
ih : ∀ s_1 ∈ f, MeasurableSet s_1
v : Set (Set α)
hv : v.Countable
vf : v ⊆ f
vu : ⋃₀ v = ⋃₀ f
⊢ MeasurableSet (⋃₀ v)

tactic: exact @MeasurableSet.sUnion α (generateFrom s) _ hv fun x xv => ih _ (vf xv)
state_before: case sUnion.intro.intro.intro
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
s : Set (Set α)
t : TopologicalSpace α
inst✝ : SecondCountableTopology α
hs : t = TopologicalSpace.generateFrom s
u : Set α
f : Set (Set α)
hf : ∀ s_1 ∈ f, GenerateOpen s s_1
ih : ∀ s_1 ∈ f, MeasurableSet s_1
v : Set (Set α)
hv : v.Countable
vf : v ⊆ f
vu : ⋃₀ v = ⋃₀ f
⊢ MeasurableSet (⋃₀ v)
state_after: no goals

tactic: rwa [hs]
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
s : Set (Set α)
t : TopologicalSpace α
inst✝ : SecondCountableTopology α
hs : t = TopologicalSpace.generateFrom s
u : Set α
f : Set (Set α)
hf : ∀ s_1 ∈ f, GenerateOpen s s_1
ih : ∀ s_1 ∈ f, MeasurableSet s_1
⊢ ∀ s ∈ f, IsOpen s
state_after: no goals

tactic: exact GenerateOpen.basic _ hu
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
s : Set (Set α)
t : TopologicalSpace α
inst✝ : SecondCountableTopology α
hs : t = TopologicalSpace.generateFrom s
u : Set α
hu : u ∈ s
⊢ TopologicalSpace.IsOpen u
state_after: no goals