-- Mathlib/MeasureTheory/Function/UniformIntegrable.lean
theorem tendsto_Lp_finite_of_tendsto_ae [IsFiniteMeasure μ] (hp : 1 ≤ p) (hp' : p ≠ ∞)
    {f : ℕ → α → β} {g : α → β} (hf : ∀ n, AEStronglyMeasurable (f n) μ) (hg : MemLp g p μ)
    (hui : UnifIntegrable f p μ) (hfg : ∀ᵐ x ∂μ, Tendsto (fun n => f n x) atTop (𝓝 (g x))) :
    Tendsto (fun n => eLpNorm (f n - g) p μ) atTop (𝓝 0)

Proof state:
case h
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup β
p : ℝ≥0∞
inst✝ : IsFiniteMeasure μ
hp : 1 ≤ p
hp' : p ≠ ⊤
f : ℕ → α → β
g : α → β
hf : ∀ (n : ℕ), AEStronglyMeasurable (f n) μ
hg : MemLp g p μ
hui : UnifIntegrable f p μ
hfg : ∀ᵐ (x : α) ∂μ, Tendsto (fun n => f n x) atTop (𝓝 (g x))
this : ∀ (n : ℕ), eLpNorm (f n - g) p μ = eLpNorm (AEStronglyMeasurable.mk (f n) ⋯ - AEStronglyMeasurable.mk g ⋯) p μ
h_ae_forall_eq : ∀ᵐ (x : α) ∂μ, ∀ (n : ℕ), f n x = AEStronglyMeasurable.mk (f n) ⋯ x
x : α
hx_tendsto : Tendsto (fun n => f n x) atTop (𝓝 (g x))
hxf_eq : ∀ (n : ℕ), f n x = AEStronglyMeasurable.mk (f n) ⋯ x
hxg_eq : g x = AEStronglyMeasurable.mk g ⋯ x
⊢ Tendsto (fun n => AEStronglyMeasurable.mk (f n) ⋯ x) atTop (𝓝 (g x))

Tactic:
convert hx_tendsto using 1

Result:
case h.e'_3
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup β
p : ℝ≥0∞
inst✝ : IsFiniteMeasure μ
hp : 1 ≤ p
hp' : p ≠ ⊤
f : ℕ → α → β
g : α → β
hf : ∀ (n : ℕ), AEStronglyMeasurable (f n) μ
hg : MemLp g p μ
hui : UnifIntegrable f p μ
hfg : ∀ᵐ (x : α) ∂μ, Tendsto (fun n => f n x) atTop (𝓝 (g x))
this : ∀ (n : ℕ), eLpNorm (f n - g) p μ = eLpNorm (AEStronglyMeasurable.mk (f n) ⋯ - AEStronglyMeasurable.mk g ⋯) p μ
h_ae_forall_eq : ∀ᵐ (x : α) ∂μ, ∀ (n : ℕ), f n x = AEStronglyMeasurable.mk (f n) ⋯ x
x : α
hx_tendsto : Tendsto (fun n => f n x) atTop (𝓝 (g x))
hxf_eq : ∀ (n : ℕ), f n x = AEStronglyMeasurable.mk (f n) ⋯ x
hxg_eq : g x = AEStronglyMeasurable.mk g ⋯ x
⊢ (fun n => AEStronglyMeasurable.mk (f n) ⋯ x) = fun n => f n x

Proof state:
case h.e'_3
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup β
p : ℝ≥0∞
inst✝ : IsFiniteMeasure μ
hp : 1 ≤ p
hp' : p ≠ ⊤
f : ℕ → α → β
g : α → β
hf : ∀ (n : ℕ), AEStronglyMeasurable (f n) μ
hg : MemLp g p μ
hui : UnifIntegrable f p μ
hfg : ∀ᵐ (x : α) ∂μ, Tendsto (fun n => f n x) atTop (𝓝 (g x))
this : ∀ (n : ℕ), eLpNorm (f n - g) p μ = eLpNorm (AEStronglyMeasurable.mk (f n) ⋯ - AEStronglyMeasurable.mk g ⋯) p μ
h_ae_forall_eq : ∀ᵐ (x : α) ∂μ, ∀ (n : ℕ), f n x = AEStronglyMeasurable.mk (f n) ⋯ x
x : α
hx_tendsto : Tendsto (fun n => f n x) atTop (𝓝 (g x))
hxf_eq : ∀ (n : ℕ), f n x = AEStronglyMeasurable.mk (f n) ⋯ x
hxg_eq : g x = AEStronglyMeasurable.mk g ⋯ x
⊢ (fun n => AEStronglyMeasurable.mk (f n) ⋯ x) = fun n => f n x

Tactic:
ext1 n

Result:
case h.e'_3.h
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup β
p : ℝ≥0∞
inst✝ : IsFiniteMeasure μ
hp : 1 ≤ p
hp' : p ≠ ⊤
f : ℕ → α → β
g : α → β
hf : ∀ (n : ℕ), AEStronglyMeasurable (f n) μ
hg : MemLp g p μ
hui : UnifIntegrable f p μ
hfg : ∀ᵐ (x : α) ∂μ, Tendsto (fun n => f n x) atTop (𝓝 (g x))
this : ∀ (n : ℕ), eLpNorm (f n - g) p μ = eLpNorm (AEStronglyMeasurable.mk (f n) ⋯ - AEStronglyMeasurable.mk g ⋯) p μ
h_ae_forall_eq : ∀ᵐ (x : α) ∂μ, ∀ (n : ℕ), f n x = AEStronglyMeasurable.mk (f n) ⋯ x
x : α
hx_tendsto : Tendsto (fun n => f n x) atTop (𝓝 (g x))
hxf_eq : ∀ (n : ℕ), f n x = AEStronglyMeasurable.mk (f n) ⋯ x
hxg_eq : g x = AEStronglyMeasurable.mk g ⋯ x
n : ℕ
⊢ AEStronglyMeasurable.mk (f n) ⋯ x = f n x

Proof state:
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup β
p : ℝ≥0∞
inst✝ : IsFiniteMeasure μ
hp : 1 ≤ p
hp' : p ≠ ⊤
f : ℕ → α → β
g : α → β
hf : ∀ (n : ℕ), AEStronglyMeasurable (f n) μ
hg : MemLp g p μ
hui : UnifIntegrable f p μ
hfg : ∀ᵐ (x : α) ∂μ, Tendsto (fun n => f n x) atTop (𝓝 (g x))
this : ∀ (n : ℕ), eLpNorm (f n - g) p μ = eLpNorm (AEStronglyMeasurable.mk (f n) ⋯ - AEStronglyMeasurable.mk g ⋯) p μ
⊢ Tendsto (fun n => eLpNorm (AEStronglyMeasurable.mk (f n) ⋯ - AEStronglyMeasurable.mk g ⋯) p μ) atTop (𝓝 0)

Tactic:
refine tendsto_Lp_finite_of_tendsto_ae_of_meas hp hp' (fun n => (hf n).stronglyMeasurable_mk)
  hg.1.stronglyMeasurable_mk (hg.ae_eq hg.1.ae_eq_mk) (hui.ae_eq fun n => (hf n).ae_eq_mk) ?_

Result:
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup β
p : ℝ≥0∞
inst✝ : IsFiniteMeasure μ
hp : 1 ≤ p
hp' : p ≠ ⊤
f : ℕ → α → β
g : α → β
hf : ∀ (n : ℕ), AEStronglyMeasurable (f n) μ
hg : MemLp g p μ
hui : UnifIntegrable f p μ
hfg : ∀ᵐ (x : α) ∂μ, Tendsto (fun n => f n x) atTop (𝓝 (g x))
this : ∀ (n : ℕ), eLpNorm (f n - g) p μ = eLpNorm (AEStronglyMeasurable.mk (f n) ⋯ - AEStronglyMeasurable.mk g ⋯) p μ
⊢ ∀ᵐ (x : α) ∂μ, Tendsto (fun n => AEStronglyMeasurable.mk (f n) ⋯ x) atTop (𝓝 (AEStronglyMeasurable.mk g ⋯ x))

Proof state:
case h
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup β
p : ℝ≥0∞
inst✝ : IsFiniteMeasure μ
hp : 1 ≤ p
hp' : p ≠ ⊤
f : ℕ → α → β
g : α → β
hf : ∀ (n : ℕ), AEStronglyMeasurable (f n) μ
hg : MemLp g p μ
hui : UnifIntegrable f p μ
hfg : ∀ᵐ (x : α) ∂μ, Tendsto (fun n => f n x) atTop (𝓝 (g x))
this : ∀ (n : ℕ), eLpNorm (f n - g) p μ = eLpNorm (AEStronglyMeasurable.mk (f n) ⋯ - AEStronglyMeasurable.mk g ⋯) p μ
h_ae_forall_eq : ∀ᵐ (x : α) ∂μ, ∀ (n : ℕ), f n x = AEStronglyMeasurable.mk (f n) ⋯ x
x : α
hx_tendsto : Tendsto (fun n => f n x) atTop (𝓝 (g x))
hxf_eq : ∀ (n : ℕ), f n x = AEStronglyMeasurable.mk (f n) ⋯ x
hxg_eq : g x = AEStronglyMeasurable.mk g ⋯ x
⊢ Tendsto (fun n => AEStronglyMeasurable.mk (f n) ⋯ x) atTop (𝓝 (AEStronglyMeasurable.mk g ⋯ x))

Tactic:
rw [← hxg_eq]

Result:
case h
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup β
p : ℝ≥0∞
inst✝ : IsFiniteMeasure μ
hp : 1 ≤ p
hp' : p ≠ ⊤
f : ℕ → α → β
g : α → β
hf : ∀ (n : ℕ), AEStronglyMeasurable (f n) μ
hg : MemLp g p μ
hui : UnifIntegrable f p μ
hfg : ∀ᵐ (x : α) ∂μ, Tendsto (fun n => f n x) atTop (𝓝 (g x))
this : ∀ (n : ℕ), eLpNorm (f n - g) p μ = eLpNorm (AEStronglyMeasurable.mk (f n) ⋯ - AEStronglyMeasurable.mk g ⋯) p μ
h_ae_forall_eq : ∀ᵐ (x : α) ∂μ, ∀ (n : ℕ), f n x = AEStronglyMeasurable.mk (f n) ⋯ x
x : α
hx_tendsto : Tendsto (fun n => f n x) atTop (𝓝 (g x))
hxf_eq : ∀ (n : ℕ), f n x = AEStronglyMeasurable.mk (f n) ⋯ x
hxg_eq : g x = AEStronglyMeasurable.mk g ⋯ x
⊢ Tendsto (fun n => AEStronglyMeasurable.mk (f n) ⋯ x) atTop (𝓝 (g x))

Proof state:
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup β
p : ℝ≥0∞
inst✝ : IsFiniteMeasure μ
hp : 1 ≤ p
hp' : p ≠ ⊤
f : ℕ → α → β
g : α → β
hf : ∀ (n : ℕ), AEStronglyMeasurable (f n) μ
hg : MemLp g p μ
hui : UnifIntegrable f p μ
hfg : ∀ᵐ (x : α) ∂μ, Tendsto (fun n => f n x) atTop (𝓝 (g x))
⊢ Tendsto (fun n => eLpNorm (f n - g) p μ) atTop (𝓝 0)

Tactic:
have : ∀ n, eLpNorm (f n - g) p μ = eLpNorm ((hf n).mk (f n) - hg.1.mk g) p μ :=
  fun n => eLpNorm_congr_ae ((hf n).ae_eq_mk.sub hg.1.ae_eq_mk)

Result:
α : Type u_1
β : Type u_2
m : MeasurableSpace α
μ : Measure α
inst✝¹ : NormedAddCommGroup β
p : ℝ≥0∞
inst✝ : IsFiniteMeasure μ
hp : 1 ≤ p
hp' : p ≠ ⊤
f : ℕ → α → β
g : α → β
hf : ∀ (n : ℕ), AEStronglyMeasurable (f n) μ
hg : MemLp g p μ
hui : UnifIntegrable f p μ
hfg : ∀ᵐ (x : α) ∂μ, Tendsto (fun n => f n x) atTop (𝓝 (g x))
this : ∀ (n : ℕ), eLpNorm (f n - g) p μ = eLpNorm (AEStronglyMeasurable.mk (f n) ⋯ - AEStronglyMeasurable.mk g ⋯) p μ
⊢ Tendsto (fun n => eLpNorm (f n - g) p μ) atTop (𝓝 0)