Theorem: Measurable.add_stronglyMeasurable
File: Mathlib/MeasureTheory/Function/StronglyMeasurable/Basic.lean

Proof steps:
state_before: α✝ : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
inst✝⁷ : Countable ι
f✝ g✝ : α✝ → β
mα : MeasurableSpace α✝
inst✝⁶ : TopologicalSpace β
α : Type u_5
E : Type u_6
x✝ : MeasurableSpace α
inst✝⁵ : AddGroup E
inst✝⁴ : TopologicalSpace E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
inst✝¹ : ContinuousAdd E
inst✝ : PseudoMetrizableSpace E
g f : α → E
hg : Measurable g
hf : StronglyMeasurable f
⊢ Measurable (g + f)
state_after: case intro
α✝ : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
inst✝⁷ : Countable ι
f✝ g✝ : α✝ → β
mα : MeasurableSpace α✝
inst✝⁶ : TopologicalSpace β
α : Type u_5
E : Type u_6
x✝ : MeasurableSpace α
inst✝⁵ : AddGroup E
inst✝⁴ : TopologicalSpace E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
inst✝¹ : ContinuousAdd E
inst✝ : PseudoMetrizableSpace E
g f : α → E
hg : Measurable g
φ : ℕ → α →ₛ E
hφ : ∀ (x : α), Tendsto (fun n => ↑(φ n) x) atTop (𝓝 (f x))
⊢ Measurable (g + f)
tactic: rcases hf with ⟨φ, hφ⟩
state_before: case intro
α✝ : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
inst✝⁷ : Countable ι
f✝ g✝ : α✝ → β
mα : MeasurableSpace α✝
inst✝⁶ : TopologicalSpace β
α : Type u_5
E : Type u_6
x✝ : MeasurableSpace α
inst✝⁵ : AddGroup E
inst✝⁴ : TopologicalSpace E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
inst✝¹ : ContinuousAdd E
inst✝ : PseudoMetrizableSpace E
g f : α → E
hg : Measurable g
φ : ℕ → α →ₛ E
hφ : ∀ (x : α), Tendsto (fun n => ↑(φ n) x) atTop (𝓝 (f x))
⊢ Measurable (g + f)
state_after: case intro
α✝ : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
inst✝⁷ : Countable ι
f✝ g✝ : α✝ → β
mα : MeasurableSpace α✝
inst✝⁶ : TopologicalSpace β
α : Type u_5
E : Type u_6
x✝ : MeasurableSpace α
inst✝⁵ : AddGroup E
inst✝⁴ : TopologicalSpace E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
inst✝¹ : ContinuousAdd E
inst✝ : PseudoMetrizableSpace E
g f : α → E
hg : Measurable g
φ : ℕ → α →ₛ E
hφ : ∀ (x : α), Tendsto (fun n => ↑(φ n) x) atTop (𝓝 (f x))
this : Tendsto (fun n x => g x + ↑(φ n) x) atTop (𝓝 (g + f))
⊢ Measurable (g + f)
tactic: have : Tendsto (fun n x ↦ g x + φ n x) atTop (𝓝 (g + f)) :=
    tendsto_pi_nhds.2 (fun x ↦ tendsto_const_nhds.add (hφ x))
state_before: case intro
α✝ : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
inst✝⁷ : Countable ι
f✝ g✝ : α✝ → β
mα : MeasurableSpace α✝
inst✝⁶ : TopologicalSpace β
α : Type u_5
E : Type u_6
x✝ : MeasurableSpace α
inst✝⁵ : AddGroup E
inst✝⁴ : TopologicalSpace E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
inst✝¹ : ContinuousAdd E
inst✝ : PseudoMetrizableSpace E
g f : α → E
hg : Measurable g
φ : ℕ → α →ₛ E
hφ : ∀ (x : α), Tendsto (fun n => ↑(φ n) x) atTop (𝓝 (f x))
this : Tendsto (fun n x => g x + ↑(φ n) x) atTop (𝓝 (g + f))
⊢ Measurable (g + f)
state_after: α✝ : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
inst✝⁷ : Countable ι
f✝ g✝ : α✝ → β
mα : MeasurableSpace α✝
inst✝⁶ : TopologicalSpace β
α : Type u_5
E : Type u_6
x✝ : MeasurableSpace α
inst✝⁵ : AddGroup E
inst✝⁴ : TopologicalSpace E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
inst✝¹ : ContinuousAdd E
inst✝ : PseudoMetrizableSpace E
g f : α → E
hg : Measurable g
φ : ℕ → α →ₛ E
hφ : ∀ (x : α), Tendsto (fun n => ↑(φ n) x) atTop (𝓝 (f x))
this : Tendsto (fun n x => g x + ↑(φ n) x) atTop (𝓝 (g + f))
n : ℕ
⊢ Measurable fun x => g x + ↑(φ n) x
tactic: apply measurable_of_tendsto_metrizable (fun n ↦ ?_) this
state_before: α✝ : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
inst✝⁷ : Countable ι
f✝ g✝ : α✝ → β
mα : MeasurableSpace α✝
inst✝⁶ : TopologicalSpace β
α : Type u_5
E : Type u_6
x✝ : MeasurableSpace α
inst✝⁵ : AddGroup E
inst✝⁴ : TopologicalSpace E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
inst✝¹ : ContinuousAdd E
inst✝ : PseudoMetrizableSpace E
g f : α → E
hg : Measurable g
φ : ℕ → α →ₛ E
hφ : ∀ (x : α), Tendsto (fun n => ↑(φ n) x) atTop (𝓝 (f x))
this : Tendsto (fun n x => g x + ↑(φ n) x) atTop (𝓝 (g + f))
n : ℕ
⊢ Measurable fun x => g x + ↑(φ n) x
state_after: no goals
tactic: exact hg.add_simpleFunc _