Theorem: MeasureTheory.IsStoppingTime.measurableSet_ge'
File: Mathlib/Probability/Process/Stopping.lean

tactic: have : {ω | i ≤ τ ω} = {ω | τ ω = i} ∪ {ω | i < τ ω} := by
  ext1 ω
  simp only [le_iff_lt_or_eq, Set.mem_setOf_eq, Set.mem_union]
  rw [@eq_comm _ i, or_comm]
state_before: Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝³ : LinearOrder ι
f : Filtration ι m
τ π : Ω → ι
inst✝² : TopologicalSpace ι
inst✝¹ : OrderTopology ι
inst✝ : FirstCountableTopology ι
hτ : IsStoppingTime f τ
i : ι
⊢ MeasurableSet {ω | i ≤ τ ω}
state_after: Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝³ : LinearOrder ι
f : Filtration ι m
τ π : Ω → ι
inst✝² : TopologicalSpace ι
inst✝¹ : OrderTopology ι
inst✝ : FirstCountableTopology ι
hτ : IsStoppingTime f τ
i : ι
this : {ω | i ≤ τ ω} = {ω | τ ω = i} ∪ {ω | i < τ ω}
⊢ MeasurableSet {ω | i ≤ τ ω}

tactic: rw [this]
state_before: Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝³ : LinearOrder ι
f : Filtration ι m
τ π : Ω → ι
inst✝² : TopologicalSpace ι
inst✝¹ : OrderTopology ι
inst✝ : FirstCountableTopology ι
hτ : IsStoppingTime f τ
i : ι
this : {ω | i ≤ τ ω} = {ω | τ ω = i} ∪ {ω | i < τ ω}
⊢ MeasurableSet {ω | i ≤ τ ω}
state_after: Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝³ : LinearOrder ι
f : Filtration ι m
τ π : Ω → ι
inst✝² : TopologicalSpace ι
inst✝¹ : OrderTopology ι
inst✝ : FirstCountableTopology ι
hτ : IsStoppingTime f τ
i : ι
this : {ω | i ≤ τ ω} = {ω | τ ω = i} ∪ {ω | i < τ ω}
⊢ MeasurableSet ({ω | τ ω = i} ∪ {ω | i < τ ω})

tactic: exact (hτ.measurableSet_eq' i).union (hτ.measurableSet_gt' i)
state_before: Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝³ : LinearOrder ι
f : Filtration ι m
τ π : Ω → ι
inst✝² : TopologicalSpace ι
inst✝¹ : OrderTopology ι
inst✝ : FirstCountableTopology ι
hτ : IsStoppingTime f τ
i : ι
this : {ω | i ≤ τ ω} = {ω | τ ω = i} ∪ {ω | i < τ ω}
⊢ MeasurableSet ({ω | τ ω = i} ∪ {ω | i < τ ω})
state_after: no goals

tactic: ext1 ω
state_before: Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝³ : LinearOrder ι
f : Filtration ι m
τ π : Ω → ι
inst✝² : TopologicalSpace ι
inst✝¹ : OrderTopology ι
inst✝ : FirstCountableTopology ι
hτ : IsStoppingTime f τ
i : ι
⊢ {ω | i ≤ τ ω} = {ω | τ ω = i} ∪ {ω | i < τ ω}
state_after: case h
Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝³ : LinearOrder ι
f : Filtration ι m
τ π : Ω → ι
inst✝² : TopologicalSpace ι
inst✝¹ : OrderTopology ι
inst✝ : FirstCountableTopology ι
hτ : IsStoppingTime f τ
i : ι
ω : Ω
⊢ ω ∈ {ω | i ≤ τ ω} ↔ ω ∈ {ω | τ ω = i} ∪ {ω | i < τ ω}

tactic: simp only [le_iff_lt_or_eq, Set.mem_setOf_eq, Set.mem_union]
state_before: case h
Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝³ : LinearOrder ι
f : Filtration ι m
τ π : Ω → ι
inst✝² : TopologicalSpace ι
inst✝¹ : OrderTopology ι
inst✝ : FirstCountableTopology ι
hτ : IsStoppingTime f τ
i : ι
ω : Ω
⊢ ω ∈ {ω | i ≤ τ ω} ↔ ω ∈ {ω | τ ω = i} ∪ {ω | i < τ ω}
state_after: case h
Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝³ : LinearOrder ι
f : Filtration ι m
τ π : Ω → ι
inst✝² : TopologicalSpace ι
inst✝¹ : OrderTopology ι
inst✝ : FirstCountableTopology ι
hτ : IsStoppingTime f τ
i : ι
ω : Ω
⊢ i < τ ω ∨ i = τ ω ↔ τ ω = i ∨ i < τ ω

tactic: rw [@eq_comm _ i, or_comm]
state_before: case h
Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝³ : LinearOrder ι
f : Filtration ι m
τ π : Ω → ι
inst✝² : TopologicalSpace ι
inst✝¹ : OrderTopology ι
inst✝ : FirstCountableTopology ι
hτ : IsStoppingTime f τ
i : ι
ω : Ω
⊢ i < τ ω ∨ i = τ ω ↔ τ ω = i ∨ i < τ ω
state_after: no goals