-- Mathlib/Probability/Integration.lean
theorem lintegral_mul_eq_lintegral_mul_lintegral_of_independent_measurableSpace
    {Mf Mg mΩ : MeasurableSpace Ω} {μ : Measure Ω} (hMf : Mf ≤ mΩ) (hMg : Mg ≤ mΩ)
    (h_ind : Indep Mf Mg μ) (h_meas_f : Measurable[Mf] f) (h_meas_g : Measurable[Mg] g) :
    ∫⁻ ω, f ω * g ω ∂μ = (∫⁻ ω, f ω ∂μ) * ∫⁻ ω, g ω ∂μ

Proof state:
case h_add
Ω : Type u_1
f : Ω → ℝ≥0∞
Mf Mg mΩ : MeasurableSpace Ω
μ : Measure Ω
hMf : Mf ≤ mΩ
hMg : Mg ≤ mΩ
h_ind : Indep Mf Mg μ
h_meas_f : Measurable f
h_measM_f : Measurable f
f' g : Ω → ℝ≥0∞
a✝¹ : Disjoint (Function.support f') (Function.support g)
h_measMg_f' : Measurable f'
a✝ : Measurable g
h_ind_f' : ∫⁻ (ω : Ω), f ω * f' ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), f' ω ∂μ
h_ind_g' : ∫⁻ (ω : Ω), f ω * g ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), g ω ∂μ
h_measM_f' : Measurable f'
⊢ ∫⁻ (ω : Ω), f ω * f' ω + f ω * g ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), f' ω + g ω ∂μ

Tactic:
rw [lintegral_add_left h_measM_f', lintegral_add_left (h_measM_f.mul h_measM_f'), left_distrib,
  h_ind_f', h_ind_g']

Result:
no goals

Proof state:
case h_iSup
Ω : Type u_1
f : Ω → ℝ≥0∞
Mf Mg mΩ : MeasurableSpace Ω
μ : Measure Ω
hMf : Mf ≤ mΩ
hMg : Mg ≤ mΩ
h_ind : Indep Mf Mg μ
h_meas_f : Measurable f
h_measM_f : Measurable f
f' : ℕ → Ω → ℝ≥0∞
h_meas_f' : ∀ (n : ℕ), Measurable (f' n)
h_mono_f' : Monotone f'
h_ind_f' : ∀ (n : ℕ), ∫⁻ (ω : Ω), f ω * f' n ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), f' n ω ∂μ
⊢ ∫⁻ (ω : Ω), f ω * (fun x => ⨆ n, f' n x) ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), (fun x => ⨆ n, f' n x) ω ∂μ

Tactic:
have h_measM_f' : ∀ n, Measurable (f' n) := fun n => (h_meas_f' n).mono hMg le_rfl

Result:
case h_iSup
Ω : Type u_1
f : Ω → ℝ≥0∞
Mf Mg mΩ : MeasurableSpace Ω
μ : Measure Ω
hMf : Mf ≤ mΩ
hMg : Mg ≤ mΩ
h_ind : Indep Mf Mg μ
h_meas_f : Measurable f
h_measM_f : Measurable f
f' : ℕ → Ω → ℝ≥0∞
h_meas_f' : ∀ (n : ℕ), Measurable (f' n)
h_mono_f' : Monotone f'
h_ind_f' : ∀ (n : ℕ), ∫⁻ (ω : Ω), f ω * f' n ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), f' n ω ∂μ
h_measM_f' : ∀ (n : ℕ), Measurable (f' n)
⊢ ∫⁻ (ω : Ω), f ω * (fun x => ⨆ n, f' n x) ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), (fun x => ⨆ n, f' n x) ω ∂μ

Proof state:
case h_iSup
Ω : Type u_1
f : Ω → ℝ≥0∞
Mf Mg mΩ : MeasurableSpace Ω
μ : Measure Ω
hMf : Mf ≤ mΩ
hMg : Mg ≤ mΩ
h_ind : Indep Mf Mg μ
h_meas_f : Measurable f
h_measM_f : Measurable f
⊢ ∀ ⦃f_1 : ℕ → Ω → ℝ≥0∞⦄,
    (∀ (n : ℕ), Measurable (f_1 n)) →
      Monotone f_1 →
        (∀ (n : ℕ), ∫⁻ (ω : Ω), f ω * f_1 n ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), f_1 n ω ∂μ) →
          ∫⁻ (ω : Ω), f ω * (fun x => ⨆ n, f_1 n x) ω ∂μ =
            (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), (fun x => ⨆ n, f_1 n x) ω ∂μ

Tactic:
intro f' h_meas_f' h_mono_f' h_ind_f'

Result:
case h_iSup
Ω : Type u_1
f : Ω → ℝ≥0∞
Mf Mg mΩ : MeasurableSpace Ω
μ : Measure Ω
hMf : Mf ≤ mΩ
hMg : Mg ≤ mΩ
h_ind : Indep Mf Mg μ
h_meas_f : Measurable f
h_measM_f : Measurable f
f' : ℕ → Ω → ℝ≥0∞
h_meas_f' : ∀ (n : ℕ), Measurable (f' n)
h_mono_f' : Monotone f'
h_ind_f' : ∀ (n : ℕ), ∫⁻ (ω : Ω), f ω * f' n ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), f' n ω ∂μ
⊢ ∫⁻ (ω : Ω), f ω * (fun x => ⨆ n, f' n x) ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), (fun x => ⨆ n, f' n x) ω ∂μ

Proof state:
Ω : Type u_1
f : Ω → ℝ≥0∞
Mf Mg mΩ : MeasurableSpace Ω
μ : Measure Ω
hMf : Mf ≤ mΩ
hMg : Mg ≤ mΩ
h_ind : Indep Mf Mg μ
h_meas_f : Measurable f
⊢ ∀ {g : Ω → ℝ≥0∞}, Measurable g → ∫⁻ (ω : Ω), f ω * g ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), g ω ∂μ

Tactic:
have h_measM_f : Measurable f := h_meas_f.mono hMf le_rfl

Result:
Ω : Type u_1
f : Ω → ℝ≥0∞
Mf Mg mΩ : MeasurableSpace Ω
μ : Measure Ω
hMf : Mf ≤ mΩ
hMg : Mg ≤ mΩ
h_ind : Indep Mf Mg μ
h_meas_f : Measurable f
h_measM_f : Measurable f
⊢ ∀ {g : Ω → ℝ≥0∞}, Measurable g → ∫⁻ (ω : Ω), f ω * g ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), g ω ∂μ

Proof state:
case h_iSup
Ω : Type u_1
f : Ω → ℝ≥0∞
Mf Mg mΩ : MeasurableSpace Ω
μ : Measure Ω
hMf : Mf ≤ mΩ
hMg : Mg ≤ mΩ
h_ind : Indep Mf Mg μ
h_meas_f : Measurable f
h_measM_f : Measurable f
f' : ℕ → Ω → ℝ≥0∞
h_meas_f' : ∀ (n : ℕ), Measurable (f' n)
h_mono_f' : Monotone f'
h_ind_f' : ∀ (n : ℕ), ∫⁻ (ω : Ω), f ω * f' n ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), f' n ω ∂μ
h_measM_f' : ∀ (n : ℕ), Measurable (f' n)
⊢ ∫⁻ (ω : Ω), f ω * (fun x => ⨆ n, f' n x) ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), (fun x => ⨆ n, f' n x) ω ∂μ

Tactic:
simp_rw [ENNReal.mul_iSup]

Result:
case h_iSup
Ω : Type u_1
f : Ω → ℝ≥0∞
Mf Mg mΩ : MeasurableSpace Ω
μ : Measure Ω
hMf : Mf ≤ mΩ
hMg : Mg ≤ mΩ
h_ind : Indep Mf Mg μ
h_meas_f : Measurable f
h_measM_f : Measurable f
f' : ℕ → Ω → ℝ≥0∞
h_meas_f' : ∀ (n : ℕ), Measurable (f' n)
h_mono_f' : Monotone f'
h_ind_f' : ∀ (n : ℕ), ∫⁻ (ω : Ω), f ω * f' n ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), f' n ω ∂μ
h_measM_f' : ∀ (n : ℕ), Measurable (f' n)
⊢ ∫⁻ (ω : Ω), ⨆ i, f ω * f' i ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), ⨆ n, f' n ω ∂μ

Proof state:
Ω : Type u_1
f : Ω → ℝ≥0∞
Mf Mg mΩ : MeasurableSpace Ω
μ : Measure Ω
hMf : Mf ≤ mΩ
hMg : Mg ≤ mΩ
h_ind : Indep Mf Mg μ
h_meas_f : Measurable f
h_measM_f : Measurable f
⊢ ∀ {g : Ω → ℝ≥0∞}, Measurable g → ∫⁻ (ω : Ω), f ω * g ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), g ω ∂μ

Tactic:
apply @Measurable.ennreal_induction _ Mg

Result:
case h_ind
Ω : Type u_1
f : Ω → ℝ≥0∞
Mf Mg mΩ : MeasurableSpace Ω
μ : Measure Ω
hMf : Mf ≤ mΩ
hMg : Mg ≤ mΩ
h_ind : Indep Mf Mg μ
h_meas_f : Measurable f
h_measM_f : Measurable f
⊢ ∀ (c : ℝ≥0∞) ⦃s : Set Ω⦄,
    MeasurableSet s →
      ∫⁻ (ω : Ω), f ω * s.indicator (fun x => c) ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), s.indicator (fun x => c) ω ∂μ

case h_add
Ω : Type u_1
f : Ω → ℝ≥0∞
Mf Mg mΩ : MeasurableSpace Ω
μ : Measure Ω
hMf : Mf ≤ mΩ
hMg : Mg ≤ mΩ
h_ind : Indep Mf Mg μ
h_meas_f : Measurable f
h_measM_f : Measurable f
⊢ ∀ ⦃f_1 g : Ω → ℝ≥0∞⦄,
    Disjoint (Function.support f_1) (Function.support g) →
      Measurable f_1 →
        Measurable g →
          ∫⁻ (ω : Ω), f ω * f_1 ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), f_1 ω ∂μ →
            ∫⁻ (ω : Ω), f ω * g ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), g ω ∂μ →
              ∫⁻ (ω : Ω), f ω * (f_1 + g) ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), (f_1 + g) ω ∂μ

case h_iSup
Ω : Type u_1
f : Ω → ℝ≥0∞
Mf Mg mΩ : MeasurableSpace Ω
μ : Measure Ω
hMf : Mf ≤ mΩ
hMg : Mg ≤ mΩ
h_ind : Indep Mf Mg μ
h_meas_f : Measurable f
h_measM_f : Measurable f
⊢ ∀ ⦃f_1 : ℕ → Ω → ℝ≥0∞⦄,
    (∀ (n : ℕ), Measurable (f_1 n)) →
      Monotone f_1 →
        (∀ (n : ℕ), ∫⁻ (ω : Ω), f ω * f_1 n ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), f_1 n ω ∂μ) →
          ∫⁻ (ω : Ω), f ω * (fun x => ⨆ n, f_1 n x) ω ∂μ =
            (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), (fun x => ⨆ n, f_1 n x) ω ∂μ

Proof state:
case h_iSup
Ω : Type u_1
f : Ω → ℝ≥0∞
Mf Mg mΩ : MeasurableSpace Ω
μ : Measure Ω
hMf : Mf ≤ mΩ
hMg : Mg ≤ mΩ
h_ind : Indep Mf Mg μ
h_meas_f : Measurable f
h_measM_f : Measurable f
f' : ℕ → Ω → ℝ≥0∞
h_meas_f' : ∀ (n : ℕ), Measurable (f' n)
h_mono_f' : Monotone f'
h_ind_f' : ∀ (n : ℕ), ∫⁻ (ω : Ω), f ω * f' n ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), f' n ω ∂μ
h_measM_f' : ∀ (n : ℕ), Measurable (f' n)
⊢ ⨆ n, ∫⁻ (a : Ω), f a * f' n a ∂μ = ⨆ i, (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (a : Ω), f' i a ∂μ

Tactic:
simp_rw [← h_ind_f']

Result:
no goals

Proof state:
case h_iSup.hf
Ω : Type u_1
f : Ω → ℝ≥0∞
Mf Mg mΩ : MeasurableSpace Ω
μ : Measure Ω
hMf : Mf ≤ mΩ
hMg : Mg ≤ mΩ
h_ind : Indep Mf Mg μ
h_meas_f : Measurable f
h_measM_f : Measurable f
f' : ℕ → Ω → ℝ≥0∞
h_meas_f' : ∀ (n : ℕ), Measurable (f' n)
h_mono_f' : Monotone f'
h_ind_f' : ∀ (n : ℕ), ∫⁻ (ω : Ω), f ω * f' n ω ∂μ = (∫⁻ (ω : Ω), f ω ∂μ) * ∫⁻ (ω : Ω), f' n ω ∂μ
h_measM_f' : ∀ (n : ℕ), Measurable (f' n)
⊢ ∀ (n : ℕ), Measurable fun ω => f ω * f' n ω

Tactic:
exact fun n => h_measM_f.mul (h_measM_f' n)

Result:
no goals