Theorem: MeasureTheory.Measure.OuterRegular.map
File: Mathlib/MeasureTheory/Measure/Regular.lean

Proof steps:
state_before: α : Type u_1
β : Type u_2
inst✝⁶ : MeasurableSpace α
inst✝⁵ : TopologicalSpace α
μ✝ : Measure α
inst✝⁴ : OpensMeasurableSpace α
inst✝³ : MeasurableSpace β
inst✝² : TopologicalSpace β
inst✝¹ : BorelSpace β
f : α ≃ₜ β
μ : Measure α
inst✝ : μ.OuterRegular
⊢ (map (⇑f) μ).OuterRegular
state_after: α : Type u_1
β : Type u_2
inst✝⁶ : MeasurableSpace α
inst✝⁵ : TopologicalSpace α
μ✝ : Measure α
inst✝⁴ : OpensMeasurableSpace α
inst✝³ : MeasurableSpace β
inst✝² : TopologicalSpace β
inst✝¹ : BorelSpace β
f : α ≃ₜ β
μ : Measure α
inst✝ : μ.OuterRegular
A : Set β
hA : MeasurableSet A
r : ℝ≥0∞
hr : r > (map (⇑f) μ) A
⊢ ∃ U ⊇ A, IsOpen U ∧ (map (⇑f) μ) U < r
tactic: refine ⟨fun A hA r hr => ?_⟩
state_before: α : Type u_1
β : Type u_2
inst✝⁶ : MeasurableSpace α
inst✝⁵ : TopologicalSpace α
μ✝ : Measure α
inst✝⁴ : OpensMeasurableSpace α
inst✝³ : MeasurableSpace β
inst✝² : TopologicalSpace β
inst✝¹ : BorelSpace β
f : α ≃ₜ β
μ : Measure α
inst✝ : μ.OuterRegular
A : Set β
hA : MeasurableSet A
r : ℝ≥0∞
hr : r > (map (⇑f) μ) A
⊢ ∃ U ⊇ A, IsOpen U ∧ (map (⇑f) μ) U < r
state_after: α : Type u_1
β : Type u_2
inst✝⁶ : MeasurableSpace α
inst✝⁵ : TopologicalSpace α
μ✝ : Measure α
inst✝⁴ : OpensMeasurableSpace α
inst✝³ : MeasurableSpace β
inst✝² : TopologicalSpace β
inst✝¹ : BorelSpace β
f : α ≃ₜ β
μ : Measure α
inst✝ : μ.OuterRegular
A : Set β
hA : MeasurableSet A
r : ℝ≥0∞
hr : r > μ (⇑f.symm '' A)
⊢ ∃ U ⊇ A, IsOpen U ∧ (map (⇑f) μ) U < r
tactic: rw [map_apply f.measurable hA, ← f.image_symm] at hr
state_before: α : Type u_1
β : Type u_2
inst✝⁶ : MeasurableSpace α
inst✝⁵ : TopologicalSpace α
μ✝ : Measure α
inst✝⁴ : OpensMeasurableSpace α
inst✝³ : MeasurableSpace β
inst✝² : TopologicalSpace β
inst✝¹ : BorelSpace β
f : α ≃ₜ β
μ : Measure α
inst✝ : μ.OuterRegular
A : Set β
hA : MeasurableSet A
r : ℝ≥0∞
hr : r > μ (⇑f.symm '' A)
⊢ ∃ U ⊇ A, IsOpen U ∧ (map (⇑f) μ) U < r
state_after: case intro.intro.intro
α : Type u_1
β : Type u_2
inst✝⁶ : MeasurableSpace α
inst✝⁵ : TopologicalSpace α
μ✝ : Measure α
inst✝⁴ : OpensMeasurableSpace α
inst✝³ : MeasurableSpace β
inst✝² : TopologicalSpace β
inst✝¹ : BorelSpace β
f : α ≃ₜ β
μ : Measure α
inst✝ : μ.OuterRegular
A : Set β
hA : MeasurableSet A
r : ℝ≥0∞
hr : r > μ (⇑f.symm '' A)
U : Set α
hAU : U ⊇ ⇑f.symm '' A
hUo : IsOpen U
hU : μ U < r
⊢ ∃ U ⊇ A, IsOpen U ∧ (map (⇑f) μ) U < r
tactic: rcases Set.exists_isOpen_lt_of_lt _ r hr with ⟨U, hAU, hUo, hU⟩
state_before: case intro.intro.intro
α : Type u_1
β : Type u_2
inst✝⁶ : MeasurableSpace α
inst✝⁵ : TopologicalSpace α
μ✝ : Measure α
inst✝⁴ : OpensMeasurableSpace α
inst✝³ : MeasurableSpace β
inst✝² : TopologicalSpace β
inst✝¹ : BorelSpace β
f : α ≃ₜ β
μ : Measure α
inst✝ : μ.OuterRegular
A : Set β
hA : MeasurableSet A
r : ℝ≥0∞
hr : r > μ (⇑f.symm '' A)
U : Set α
hAU : U ⊇ ⇑f.symm '' A
hUo : IsOpen U
hU : μ U < r
⊢ ∃ U ⊇ A, IsOpen U ∧ (map (⇑f) μ) U < r
state_after: case intro.intro.intro
α : Type u_1
β : Type u_2
inst✝⁶ : MeasurableSpace α
inst✝⁵ : TopologicalSpace α
μ✝ : Measure α
inst✝⁴ : OpensMeasurableSpace α
inst✝³ : MeasurableSpace β
inst✝² : TopologicalSpace β
inst✝¹ : BorelSpace β
f : α ≃ₜ β
μ : Measure α
inst✝ : μ.OuterRegular
A : Set β
hA : MeasurableSet A
r : ℝ≥0∞
hr : r > μ (⇑f.symm '' A)
U : Set α
hAU : U ⊇ ⇑f.symm '' A
hUo : IsOpen U
hU : μ U < r
this : IsOpen (⇑f.symm ⁻¹' U)
⊢ ∃ U ⊇ A, IsOpen U ∧ (map (⇑f) μ) U < r
tactic: have : IsOpen (f.symm ⁻¹' U) := hUo.preimage f.symm.continuous
state_before: case intro.intro.intro
α : Type u_1
β : Type u_2
inst✝⁶ : MeasurableSpace α
inst✝⁵ : TopologicalSpace α
μ✝ : Measure α
inst✝⁴ : OpensMeasurableSpace α
inst✝³ : MeasurableSpace β
inst✝² : TopologicalSpace β
inst✝¹ : BorelSpace β
f : α ≃ₜ β
μ : Measure α
inst✝ : μ.OuterRegular
A : Set β
hA : MeasurableSet A
r : ℝ≥0∞
hr : r > μ (⇑f.symm '' A)
U : Set α
hAU : U ⊇ ⇑f.symm '' A
hUo : IsOpen U
hU : μ U < r
this : IsOpen (⇑f.symm ⁻¹' U)
⊢ ∃ U ⊇ A, IsOpen U ∧ (map (⇑f) μ) U < r
state_after: case intro.intro.intro
α : Type u_1
β : Type u_2
inst✝⁶ : MeasurableSpace α
inst✝⁵ : TopologicalSpace α
μ✝ : Measure α
inst✝⁴ : OpensMeasurableSpace α
inst✝³ : MeasurableSpace β
inst✝² : TopologicalSpace β
inst✝¹ : BorelSpace β
f : α ≃ₜ β
μ : Measure α
inst✝ : μ.OuterRegular
A : Set β
hA : MeasurableSet A
r : ℝ≥0∞
hr : r > μ (⇑f.symm '' A)
U : Set α
hAU : U ⊇ ⇑f.symm '' A
hUo : IsOpen U
hU : μ U < r
this : IsOpen (⇑f.symm ⁻¹' U)
⊢ (map (⇑f) μ) (⇑f.symm ⁻¹' U) < r
tactic: refine ⟨f.symm ⁻¹' U, image_subset_iff.1 hAU, this, ?_⟩
state_before: case intro.intro.intro
α : Type u_1
β : Type u_2
inst✝⁶ : MeasurableSpace α
inst✝⁵ : TopologicalSpace α
μ✝ : Measure α
inst✝⁴ : OpensMeasurableSpace α
inst✝³ : MeasurableSpace β
inst✝² : TopologicalSpace β
inst✝¹ : BorelSpace β
f : α ≃ₜ β
μ : Measure α
inst✝ : μ.OuterRegular
A : Set β
hA : MeasurableSet A
r : ℝ≥0∞
hr : r > μ (⇑f.symm '' A)
U : Set α
hAU : U ⊇ ⇑f.symm '' A
hUo : IsOpen U
hU : μ U < r
this : IsOpen (⇑f.symm ⁻¹' U)
⊢ (map (⇑f) μ) (⇑f.symm ⁻¹' U) < r
state_after: no goals
tactic: rwa [map_apply f.measurable this.measurableSet, f.preimage_symm, f.preimage_image]