-- Mathlib/Probability/Moments/ComplexMGF.lean
/-- If two random variables have the same moment generating function then they have
the same `integrableExpSet`. -/
lemma integrableExpSet_eq_of_mgf [IsProbabilityMeasure μ]
    (hXY : mgf X μ = mgf Y μ') :
    integrableExpSet X μ = integrableExpSet Y μ'

Proof state:
Ω : Type u_1
m : MeasurableSpace Ω
X : Ω → ℝ
μ : Measure Ω
Ω' : Type u_3
mΩ' : MeasurableSpace Ω'
Y : Ω' → ℝ
μ' : Measure Ω'
inst✝ : IsProbabilityMeasure μ
hXY : mgf X μ = mgf Y μ'
⊢ μ = 0 ↔ μ' = 0

Tactic:
simp only [IsProbabilityMeasure.ne_zero, false_iff]

Result:
Ω : Type u_1
m : MeasurableSpace Ω
X : Ω → ℝ
μ : Measure Ω
Ω' : Type u_3
mΩ' : MeasurableSpace Ω'
Y : Ω' → ℝ
μ' : Measure Ω'
inst✝ : IsProbabilityMeasure μ
hXY : mgf X μ = mgf Y μ'
⊢ ¬μ' = 0

Proof state:
Ω : Type u_1
m : MeasurableSpace Ω
X : Ω → ℝ
μ : Measure Ω
Ω' : Type u_3
mΩ' : MeasurableSpace Ω'
Y : Ω' → ℝ
μ' : Measure Ω'
inst✝ : IsProbabilityMeasure μ
hXY : mgf X μ = mgf Y μ'
this : mgf Y μ' 0 ≠ 0
⊢ ¬μ' = 0

Tactic:
intro h_contra

Result:
Ω : Type u_1
m : MeasurableSpace Ω
X : Ω → ℝ
μ : Measure Ω
Ω' : Type u_3
mΩ' : MeasurableSpace Ω'
Y : Ω' → ℝ
μ' : Measure Ω'
inst✝ : IsProbabilityMeasure μ
hXY : mgf X μ = mgf Y μ'
this : mgf Y μ' 0 ≠ 0
h_contra : μ' = 0
⊢ False

Proof state:
Ω : Type u_1
m : MeasurableSpace Ω
X : Ω → ℝ
μ : Measure Ω
Ω' : Type u_3
mΩ' : MeasurableSpace Ω'
Y : Ω' → ℝ
μ' : Measure Ω'
inst✝ : IsProbabilityMeasure μ
hXY : mgf X μ = mgf Y μ'
⊢ ¬μ' = 0

Tactic:
suffices mgf Y μ' 0 ≠ 0 by
  intro h_contra
  simp [h_contra] at this

Result:
Ω : Type u_1
m : MeasurableSpace Ω
X : Ω → ℝ
μ : Measure Ω
Ω' : Type u_3
mΩ' : MeasurableSpace Ω'
Y : Ω' → ℝ
μ' : Measure Ω'
inst✝ : IsProbabilityMeasure μ
hXY : mgf X μ = mgf Y μ'
⊢ mgf Y μ' 0 ≠ 0

Proof state:
Ω : Type u_1
m : MeasurableSpace Ω
X : Ω → ℝ
μ : Measure Ω
Ω' : Type u_3
mΩ' : MeasurableSpace Ω'
Y : Ω' → ℝ
μ' : Measure Ω'
inst✝ : IsProbabilityMeasure μ
hXY : mgf X μ = mgf Y μ'
⊢ Integrable (fun ω => rexp (0 * X ω)) μ

Tactic:
simp

Result:
no goals

Proof state:
Ω : Type u_1
m : MeasurableSpace Ω
X : Ω → ℝ
μ : Measure Ω
Ω' : Type u_3
mΩ' : MeasurableSpace Ω'
Y : Ω' → ℝ
μ' : Measure Ω'
inst✝ : IsProbabilityMeasure μ
hXY : mgf X μ = mgf Y μ'
⊢ integrableExpSet X μ = integrableExpSet Y μ'

Tactic:
refine integrableExpSet_eq_of_mgf' hXY ?_

Result:
Ω : Type u_1
m : MeasurableSpace Ω
X : Ω → ℝ
μ : Measure Ω
Ω' : Type u_3
mΩ' : MeasurableSpace Ω'
Y : Ω' → ℝ
μ' : Measure Ω'
inst✝ : IsProbabilityMeasure μ
hXY : mgf X μ = mgf Y μ'
⊢ μ = 0 ↔ μ' = 0

Proof state:
Ω : Type u_1
m : MeasurableSpace Ω
X : Ω → ℝ
μ : Measure Ω
Ω' : Type u_3
mΩ' : MeasurableSpace Ω'
Y : Ω' → ℝ
μ' : Measure Ω'
inst✝ : IsProbabilityMeasure μ
hXY : mgf X μ = mgf Y μ'
⊢ mgf Y μ' 0 ≠ 0

Tactic:
rw [← hXY]

Result:
Ω : Type u_1
m : MeasurableSpace Ω
X : Ω → ℝ
μ : Measure Ω
Ω' : Type u_3
mΩ' : MeasurableSpace Ω'
Y : Ω' → ℝ
μ' : Measure Ω'
inst✝ : IsProbabilityMeasure μ
hXY : mgf X μ = mgf Y μ'
⊢ mgf X μ 0 ≠ 0

Proof state:
Ω : Type u_1
m : MeasurableSpace Ω
X : Ω → ℝ
μ : Measure Ω
Ω' : Type u_3
mΩ' : MeasurableSpace Ω'
Y : Ω' → ℝ
μ' : Measure Ω'
inst✝ : IsProbabilityMeasure μ
hXY : mgf X μ = mgf Y μ'
⊢ mgf X μ 0 ≠ 0

Tactic:
exact (mgf_pos (by simp)).ne'

Result:
no goals

Proof state:
Ω : Type u_1
m : MeasurableSpace Ω
X : Ω → ℝ
μ : Measure Ω
Ω' : Type u_3
mΩ' : MeasurableSpace Ω'
Y : Ω' → ℝ
μ' : Measure Ω'
inst✝ : IsProbabilityMeasure μ
hXY : mgf X μ = mgf Y μ'
this : mgf Y μ' 0 ≠ 0
h_contra : μ' = 0
⊢ False

Tactic:
simp [h_contra] at this

Result:
no goals