Theorem: MeasureTheory.Measure.ae_eq_image_of_ae_eq_comap
File: Mathlib/MeasureTheory/Measure/MeasureSpace.lean

Proof steps:
state_before: α : Type u_1
β✝ : Type u_2
γ : Type u_3
δ : Type u_4
ι : Type u_5
R : Type u_6
R' : Type u_7
m0 : MeasurableSpace α
inst✝² : MeasurableSpace β✝
inst✝¹ : MeasurableSpace γ
μ✝ μ₁ μ₂ μ₃ ν ν' ν₁ ν₂ : Measure α
s✝ s' t✝ : Set α
f✝ : α → β✝
β : Type u_8
inst✝ : MeasurableSpace α
mβ : MeasurableSpace β
f : α → β
μ : Measure β
hfi : Injective f
hf : ∀ (s : Set α), MeasurableSet s → NullMeasurableSet (f '' s) μ
s t : Set α
hst : s =ᶠ[ae (comap f μ)] t
⊢ f '' s =ᶠ[ae μ] f '' t
state_after: α : Type u_1
β✝ : Type u_2
γ : Type u_3
δ : Type u_4
ι : Type u_5
R : Type u_6
R' : Type u_7
m0 : MeasurableSpace α
inst✝² : MeasurableSpace β✝
inst✝¹ : MeasurableSpace γ
μ✝ μ₁ μ₂ μ₃ ν ν' ν₁ ν₂ : Measure α
s✝ s' t✝ : Set α
f✝ : α → β✝
β : Type u_8
inst✝ : MeasurableSpace α
mβ : MeasurableSpace β
f : α → β
μ : Measure β
hfi : Injective f
hf : ∀ (s : Set α), MeasurableSet s → NullMeasurableSet (f '' s) μ
s t : Set α
hst : (comap f μ) {a | ¬s a = t a} = 0
⊢ μ {a | ¬(f '' s) a = (f '' t) a} = 0
tactic: rw [EventuallyEq, ae_iff] at hst ⊢
state_before: α : Type u_1
β✝ : Type u_2
γ : Type u_3
δ : Type u_4
ι : Type u_5
R : Type u_6
R' : Type u_7
m0 : MeasurableSpace α
inst✝² : MeasurableSpace β✝
inst✝¹ : MeasurableSpace γ
μ✝ μ₁ μ₂ μ₃ ν ν' ν₁ ν₂ : Measure α
s✝ s' t✝ : Set α
f✝ : α → β✝
β : Type u_8
inst✝ : MeasurableSpace α
mβ : MeasurableSpace β
f : α → β
μ : Measure β
hfi : Injective f
hf : ∀ (s : Set α), MeasurableSet s → NullMeasurableSet (f '' s) μ
s t : Set α
hst : (comap f μ) {a | ¬s a = t a} = 0
⊢ μ {a | ¬(f '' s) a = (f '' t) a} = 0
state_after: α : Type u_1
β✝ : Type u_2
γ : Type u_3
δ : Type u_4
ι : Type u_5
R : Type u_6
R' : Type u_7
m0 : MeasurableSpace α
inst✝² : MeasurableSpace β✝
inst✝¹ : MeasurableSpace γ
μ✝ μ₁ μ₂ μ₃ ν ν' ν₁ ν₂ : Measure α
s✝ s' t✝ : Set α
f✝ : α → β✝
β : Type u_8
inst✝ : MeasurableSpace α
mβ : MeasurableSpace β
f : α → β
μ : Measure β
hfi : Injective f
hf : ∀ (s : Set α), MeasurableSet s → NullMeasurableSet (f '' s) μ
s t : Set α
hst : (comap f μ) {a | ¬s a = t a} = 0
h_eq_α : {a | ¬s a = t a} = s \ t ∪ t \ s
⊢ μ {a | ¬(f '' s) a = (f '' t) a} = 0
tactic: have h_eq_α : { a : α | ¬s a = t a } = s \ t ∪ t \ s := by
    ext1 x
    simp only [eq_iff_iff, mem_setOf_eq, mem_union, mem_diff]
    tauto
state_before: α : Type u_1
β✝ : Type u_2
γ : Type u_3
δ : Type u_4
ι : Type u_5
R : Type u_6
R' : Type u_7
m0 : MeasurableSpace α
inst✝² : MeasurableSpace β✝
inst✝¹ : MeasurableSpace γ
μ✝ μ₁ μ₂ μ₃ ν ν' ν₁ ν₂ : Measure α
s✝ s' t✝ : Set α
f✝ : α → β✝
β : Type u_8
inst✝ : MeasurableSpace α
mβ : MeasurableSpace β
f : α → β
μ : Measure β
hfi : Injective f
hf : ∀ (s : Set α), MeasurableSet s → NullMeasurableSet (f '' s) μ
s t : Set α
hst : (comap f μ) {a | ¬s a = t a} = 0
h_eq_α : {a | ¬s a = t a} = s \ t ∪ t \ s
⊢ μ {a | ¬(f '' s) a = (f '' t) a} = 0
state_after: α : Type u_1
β✝ : Type u_2
γ : Type u_3
δ : Type u_4
ι : Type u_5
R : Type u_6
R' : Type u_7
m0 : MeasurableSpace α
inst✝² : MeasurableSpace β✝
inst✝¹ : MeasurableSpace γ
μ✝ μ₁ μ₂ μ₃ ν ν' ν₁ ν₂ : Measure α
s✝ s' t✝ : Set α
f✝ : α → β✝
β : Type u_8
inst✝ : MeasurableSpace α
mβ : MeasurableSpace β
f : α → β
μ : Measure β
hfi : Injective f
hf : ∀ (s : Set α), MeasurableSet s → NullMeasurableSet (f '' s) μ
s t : Set α
hst : (comap f μ) {a | ¬s a = t a} = 0
h_eq_α : {a | ¬s a = t a} = s \ t ∪ t \ s
h_eq_β : {a | ¬(f '' s) a = (f '' t) a} = f '' s \ f '' t ∪ f '' t \ f '' s
⊢ μ {a | ¬(f '' s) a = (f '' t) a} = 0
tactic: have h_eq_β : { a : β | ¬(f '' s) a = (f '' t) a } = f '' s \ f '' t ∪ f '' t \ f '' s := by
    ext1 x
    simp only [eq_iff_iff, mem_setOf_eq, mem_union, mem_diff]
    tauto
state_before: α : Type u_1
β✝ : Type u_2
γ : Type u_3
δ : Type u_4
ι : Type u_5
R : Type u_6
R' : Type u_7
m0 : MeasurableSpace α
inst✝² : MeasurableSpace β✝
inst✝¹ : MeasurableSpace γ
μ✝ μ₁ μ₂ μ₃ ν ν' ν₁ ν₂ : Measure α
s✝ s' t✝ : Set α
f✝ : α → β✝
β : Type u_8
inst✝ : MeasurableSpace α
mβ : MeasurableSpace β
f : α → β
μ : Measure β
hfi : Injective f
hf : ∀ (s : Set α), MeasurableSet s → NullMeasurableSet (f '' s) μ
s t : Set α
hst : (comap f μ) {a | ¬s a = t a} = 0
h_eq_α : {a | ¬s a = t a} = s \ t ∪ t \ s
h_eq_β : {a | ¬(f '' s) a = (f '' t) a} = f '' s \ f '' t ∪ f '' t \ f '' s
⊢ μ {a | ¬(f '' s) a = (f '' t) a} = 0
state_after: α : Type u_1
β✝ : Type u_2
γ : Type u_3
δ : Type u_4
ι : Type u_5
R : Type u_6
R' : Type u_7
m0 : MeasurableSpace α
inst✝² : MeasurableSpace β✝
inst✝¹ : MeasurableSpace γ
μ✝ μ₁ μ₂ μ₃ ν ν' ν₁ ν₂ : Measure α
s✝ s' t✝ : Set α
f✝ : α → β✝
β : Type u_8
inst✝ : MeasurableSpace α
mβ : MeasurableSpace β
f : α → β
μ : Measure β
hfi : Injective f
hf : ∀ (s : Set α), MeasurableSet s → NullMeasurableSet (f '' s) μ
s t : Set α
hst : (comap f μ) {a | ¬s a = t a} = 0
h_eq_α : {a | ¬s a = t a} = s \ t ∪ t \ s
h_eq_β : {a | ¬(f '' s) a = (f '' t) a} = f '' (s \ t ∪ t \ s)
⊢ μ {a | ¬(f '' s) a = (f '' t) a} = 0
tactic: rw [← Set.image_diff hfi, ← Set.image_diff hfi, ← Set.image_union] at h_eq_β
state_before: α : Type u_1
β✝ : Type u_2
γ : Type u_3
δ : Type u_4
ι : Type u_5
R : Type u_6
R' : Type u_7
m0 : MeasurableSpace α
inst✝² : MeasurableSpace β✝
inst✝¹ : MeasurableSpace γ
μ✝ μ₁ μ₂ μ₃ ν ν' ν₁ ν₂ : Measure α
s✝ s' t✝ : Set α
f✝ : α → β✝
β : Type u_8
inst✝ : MeasurableSpace α
mβ : MeasurableSpace β
f : α → β
μ : Measure β
hfi : Injective f
hf : ∀ (s : Set α), MeasurableSet s → NullMeasurableSet (f '' s) μ
s t : Set α
hst : (comap f μ) {a | ¬s a = t a} = 0
h_eq_α : {a | ¬s a = t a} = s \ t ∪ t \ s
h_eq_β : {a | ¬(f '' s) a = (f '' t) a} = f '' (s \ t ∪ t \ s)
⊢ μ {a | ¬(f '' s) a = (f '' t) a} = 0
state_after: α : Type u_1
β✝ : Type u_2
γ : Type u_3
δ : Type u_4
ι : Type u_5
R : Type u_6
R' : Type u_7
m0 : MeasurableSpace α
inst✝² : MeasurableSpace β✝
inst✝¹ : MeasurableSpace γ
μ✝ μ₁ μ₂ μ₃ ν ν' ν₁ ν₂ : Measure α
s✝ s' t✝ : Set α
f✝ : α → β✝
β : Type u_8
inst✝ : MeasurableSpace α
mβ : MeasurableSpace β
f : α → β
μ : Measure β
hfi : Injective f
hf : ∀ (s : Set α), MeasurableSet s → NullMeasurableSet (f '' s) μ
s t : Set α
hst : (comap f μ) {a | ¬s a = t a} = 0
h_eq_α : {a | ¬s a = t a} = s \ t ∪ t \ s
h_eq_β : {a | ¬(f '' s) a = (f '' t) a} = f '' (s \ t ∪ t \ s)
⊢ μ (f '' (s \ t ∪ t \ s)) = 0
tactic: rw [h_eq_β]
state_before: α : Type u_1
β✝ : Type u_2
γ : Type u_3
δ : Type u_4
ι : Type u_5
R : Type u_6
R' : Type u_7
m0 : MeasurableSpace α
inst✝² : MeasurableSpace β✝
inst✝¹ : MeasurableSpace γ
μ✝ μ₁ μ₂ μ₃ ν ν' ν₁ ν₂ : Measure α
s✝ s' t✝ : Set α
f✝ : α → β✝
β : Type u_8
inst✝ : MeasurableSpace α
mβ : MeasurableSpace β
f : α → β
μ : Measure β
hfi : Injective f
hf : ∀ (s : Set α), MeasurableSet s → NullMeasurableSet (f '' s) μ
s t : Set α
hst : (comap f μ) {a | ¬s a = t a} = 0
h_eq_α : {a | ¬s a = t a} = s \ t ∪ t \ s
h_eq_β : {a | ¬(f '' s) a = (f '' t) a} = f '' (s \ t ∪ t \ s)
⊢ μ (f '' (s \ t ∪ t \ s)) = 0
state_after: α : Type u_1
β✝ : Type u_2
γ : Type u_3
δ : Type u_4
ι : Type u_5
R : Type u_6
R' : Type u_7
m0 : MeasurableSpace α
inst✝² : MeasurableSpace β✝
inst✝¹ : MeasurableSpace γ
μ✝ μ₁ μ₂ μ₃ ν ν' ν₁ ν₂ : Measure α
s✝ s' t✝ : Set α
f✝ : α → β✝
β : Type u_8
inst✝ : MeasurableSpace α
mβ : MeasurableSpace β
f : α → β
μ : Measure β
hfi : Injective f
hf : ∀ (s : Set α), MeasurableSet s → NullMeasurableSet (f '' s) μ
s t : Set α
hst : (comap f μ) (s \ t ∪ t \ s) = 0
h_eq_α : {a | ¬s a = t a} = s \ t ∪ t \ s
h_eq_β : {a | ¬(f '' s) a = (f '' t) a} = f '' (s \ t ∪ t \ s)
⊢ μ (f '' (s \ t ∪ t \ s)) = 0
tactic: rw [h_eq_α] at hst
state_before: α : Type u_1
β✝ : Type u_2
γ : Type u_3
δ : Type u_4
ι : Type u_5
R : Type u_6
R' : Type u_7
m0 : MeasurableSpace α
inst✝² : MeasurableSpace β✝
inst✝¹ : MeasurableSpace γ
μ✝ μ₁ μ₂ μ₃ ν ν' ν₁ ν₂ : Measure α
s✝ s' t✝ : Set α
f✝ : α → β✝
β : Type u_8
inst✝ : MeasurableSpace α
mβ : MeasurableSpace β
f : α → β
μ : Measure β
hfi : Injective f
hf : ∀ (s : Set α), MeasurableSet s → NullMeasurableSet (f '' s) μ
s t : Set α
hst : (comap f μ) (s \ t ∪ t \ s) = 0
h_eq_α : {a | ¬s a = t a} = s \ t ∪ t \ s
h_eq_β : {a | ¬(f '' s) a = (f '' t) a} = f '' (s \ t ∪ t \ s)
⊢ μ (f '' (s \ t ∪ t \ s)) = 0
state_after: no goals
tactic: exact measure_image_eq_zero_of_comap_eq_zero f μ hfi hf hst