Module: Mathlib.Probability.Kernel.IonescuTulcea.Traj

Goal state before:
pp: X : ℕ → Type u_1
inst✝¹ : (n : ℕ) → MeasurableSpace (X n)
κ : (n : ℕ) → Kernel ((i : ↥(Iic n)) → X ↑i) (X (n + 1))
inst✝ : ∀ (n : ℕ), IsMarkovKernel (κ n)
f : ℕ → ((n : ℕ) → X n) → ℝ≥0∞
a : ℕ → ℕ
hcte : ∀ (n : ℕ), DependsOn (f n) ↑(Iic (a n))
mf : ∀ (n : ℕ), Measurable (f n)
bound : ℝ≥0∞
fin_bound : bound ≠ ∞
le_bound : ∀ (n : ℕ) (x : (n : ℕ) → X n), f n x ≤ bound
k : ℕ
anti : ∀ (x : (n : ℕ) → X n), Antitone fun n ↦ lmarginalPartialTraj κ (k + 1) (a n) (f n) x
l : ((n : ℕ) → X n) → ℝ≥0∞
htendsto : ∀ (x : (n : ℕ) → X n), Tendsto (fun n ↦ lmarginalPartialTraj κ (k + 1) (a n) (f n) x) atTop (𝓝 (l x))
ε : ℝ≥0∞
y : (i : ↥(Iic k)) → X ↑i
hpos : ∀ (x : (i : ℕ) → X i) (n : ℕ), ε ≤ lmarginalPartialTraj κ k (a n) (f n) (updateFinset x (Iic k) y)
x✝ : ∀ (n : ℕ), Nonempty (X n)
F : ℕ → ((n : ℕ) → X n) → ℝ≥0∞ := fun n ↦ lmarginalPartialTraj κ (k + 1) (a n) (f n)
tendstoF : ∀ (x : (n : ℕ) → X n), Tendsto (fun x_1 ↦ F x_1 x) atTop (𝓝 (l x))
f_eq : ∀ (x : (n : ℕ) → X n) (n : ℕ), lmarginalPartialTraj κ k (a n) (f n) x = lmarginalPartialTraj κ k (k + 1) (F n) x
F_le : ∀ (n : ℕ) (x : (n : ℕ) → X n), F n x ≤ bound
⊢ ∃ z,
    ∀ (x : (i : ℕ) → X i) (n : ℕ),
      ε ≤ lmarginalPartialTraj κ (k + 1) (a n) (f n) (update (updateFinset x (Iic k) y) (k + 1) z)

Tactic:
have tendsto_int x : Tendsto (fun n ↦ lmarginalPartialTraj κ k (a n) (f n) x) atTop
      (𝓝 (lmarginalPartialTraj κ k (k + 1) l x)) := by
    simp_rw [f_eq, lmarginalPartialTraj]
    exact tendsto_lintegral_of_dominated_convergence (fun _ ↦ bound)
      (fun n ↦ (measurable_lmarginalPartialTraj _ _ (mf n)).comp measurable_updateFinset)
      (fun n ↦ Eventually.of_forall <| fun y ↦ F_le n _)
      (by simp [fin_bound]) (Eventually.of_forall (fun _ ↦ tendstoF _))

Goal state after:
X : ℕ → Type u_1
inst✝¹ : (n : ℕ) → MeasurableSpace (X n)
κ : (n : ℕ) → Kernel ((i : ↥(Iic n)) → X ↑i) (X (n + 1))
inst✝ : ∀ (n : ℕ), IsMarkovKernel (κ n)
f : ℕ → ((n : ℕ) → X n) → ℝ≥0∞
a : ℕ → ℕ
hcte : ∀ (n : ℕ), DependsOn (f n) ↑(Iic (a n))
mf : ∀ (n : ℕ), Measurable (f n)
bound : ℝ≥0∞
fin_bound : bound ≠ ∞
le_bound : ∀ (n : ℕ) (x : (n : ℕ) → X n), f n x ≤ bound
k : ℕ
anti : ∀ (x : (n : ℕ) → X n), Antitone fun n ↦ lmarginalPartialTraj κ (k + 1) (a n) (f n) x
l : ((n : ℕ) → X n) → ℝ≥0∞
htendsto : ∀ (x : (n : ℕ) → X n), Tendsto (fun n ↦ lmarginalPartialTraj κ (k + 1) (a n) (f n) x) atTop (𝓝 (l x))
ε : ℝ≥0∞
y : (i : ↥(Iic k)) → X ↑i
hpos : ∀ (x : (i : ℕ) → X i) (n : ℕ), ε ≤ lmarginalPartialTraj κ k (a n) (f n) (updateFinset x (Iic k) y)
x✝ : ∀ (n : ℕ), Nonempty (X n)
F : ℕ → ((n : ℕ) → X n) → ℝ≥0∞ := fun n ↦ lmarginalPartialTraj κ (k + 1) (a n) (f n)
tendstoF : ∀ (x : (n : ℕ) → X n), Tendsto (fun x_1 ↦ F x_1 x) atTop (𝓝 (l x))
f_eq : ∀ (x : (n : ℕ) → X n) (n : ℕ), lmarginalPartialTraj κ k (a n) (f n) x = lmarginalPartialTraj κ k (k + 1) (F n) x
F_le : ∀ (n : ℕ) (x : (n : ℕ) → X n), F n x ≤ bound
tendsto_int :
  ∀ (x : (n : ℕ) → X n),
    Tendsto (fun n ↦ lmarginalPartialTraj κ k (a n) (f n) x) atTop (𝓝 (lmarginalPartialTraj κ k (k + 1) l x))
⊢ ∃ z,
    ∀ (x : (i : ℕ) → X i) (n : ℕ),
      ε ≤ lmarginalPartialTraj κ (k + 1) (a n) (f n) (update (updateFinset x (Iic k) y) (k + 1) z)