Theorem: ENNReal.lintegral_mul_norm_pow_le
File: Mathlib/MeasureTheory/Integral/MeanInequalities.lean

Proof steps:
state_before: α✝ : Type u_1
inst✝¹ : MeasurableSpace α✝
μ✝ : Measure α✝
α : Type u_2
inst✝ : MeasurableSpace α
μ : Measure α
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
p q : ℝ
hp : 0 ≤ p
hq : 0 ≤ q
hpq : p + q = 1
⊢ ∫⁻ (a : α), f a ^ p * g a ^ q ∂μ ≤ (∫⁻ (a : α), f a ∂μ) ^ p * (∫⁻ (a : α), g a ∂μ) ^ q
state_after: case inl
α✝ : Type u_1
inst✝¹ : MeasurableSpace α✝
μ✝ : Measure α✝
α : Type u_2
inst✝ : MeasurableSpace α
μ : Measure α
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
q : ℝ
hq : 0 ≤ q
hp : 0 ≤ 0
hpq : 0 + q = 1
⊢ ∫⁻ (a : α), f a ^ 0 * g a ^ q ∂μ ≤ (∫⁻ (a : α), f a ∂μ) ^ 0 * (∫⁻ (a : α), g a ∂μ) ^ q

case inr
α✝ : Type u_1
inst✝¹ : MeasurableSpace α✝
μ✝ : Measure α✝
α : Type u_2
inst✝ : MeasurableSpace α
μ : Measure α
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
p q : ℝ
hp✝ : 0 ≤ p
hq : 0 ≤ q
hpq : p + q = 1
hp : 0 < p
⊢ ∫⁻ (a : α), f a ^ p * g a ^ q ∂μ ≤ (∫⁻ (a : α), f a ∂μ) ^ p * (∫⁻ (a : α), g a ∂μ) ^ q
tactic: rcases hp.eq_or_lt with rfl|hp
state_before: case inr
α✝ : Type u_1
inst✝¹ : MeasurableSpace α✝
μ✝ : Measure α✝
α : Type u_2
inst✝ : MeasurableSpace α
μ : Measure α
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
p q : ℝ
hp✝ : 0 ≤ p
hq : 0 ≤ q
hpq : p + q = 1
hp : 0 < p
⊢ ∫⁻ (a : α), f a ^ p * g a ^ q ∂μ ≤ (∫⁻ (a : α), f a ∂μ) ^ p * (∫⁻ (a : α), g a ∂μ) ^ q
state_after: case inr.inl
α✝ : Type u_1
inst✝¹ : MeasurableSpace α✝
μ✝ : Measure α✝
α : Type u_2
inst✝ : MeasurableSpace α
μ : Measure α
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
p : ℝ
hp✝ : 0 ≤ p
hp : 0 < p
hq : 0 ≤ 0
hpq : p + 0 = 1
⊢ ∫⁻ (a : α), f a ^ p * g a ^ 0 ∂μ ≤ (∫⁻ (a : α), f a ∂μ) ^ p * (∫⁻ (a : α), g a ∂μ) ^ 0

case inr.inr
α✝ : Type u_1
inst✝¹ : MeasurableSpace α✝
μ✝ : Measure α✝
α : Type u_2
inst✝ : MeasurableSpace α
μ : Measure α
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
p q : ℝ
hp✝ : 0 ≤ p
hq✝ : 0 ≤ q
hpq : p + q = 1
hp : 0 < p
hq : 0 < q
⊢ ∫⁻ (a : α), f a ^ p * g a ^ q ∂μ ≤ (∫⁻ (a : α), f a ∂μ) ^ p * (∫⁻ (a : α), g a ∂μ) ^ q
tactic: rcases hq.eq_or_lt with rfl|hq
state_before: case inr.inr
α✝ : Type u_1
inst✝¹ : MeasurableSpace α✝
μ✝ : Measure α✝
α : Type u_2
inst✝ : MeasurableSpace α
μ : Measure α
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
p q : ℝ
hp✝ : 0 ≤ p
hq✝ : 0 ≤ q
hpq : p + q = 1
hp : 0 < p
hq : 0 < q
⊢ ∫⁻ (a : α), f a ^ p * g a ^ q ∂μ ≤ (∫⁻ (a : α), f a ∂μ) ^ p * (∫⁻ (a : α), g a ∂μ) ^ q
state_after: case inr.inr
α✝ : Type u_1
inst✝¹ : MeasurableSpace α✝
μ✝ : Measure α✝
α : Type u_2
inst✝ : MeasurableSpace α
μ : Measure α
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
p q : ℝ
hp✝ : 0 ≤ p
hq✝ : 0 ≤ q
hpq : p + q = 1
hp : 0 < p
hq : 0 < q
h2p : 1 < 1 / p
⊢ ∫⁻ (a : α), f a ^ p * g a ^ q ∂μ ≤ (∫⁻ (a : α), f a ∂μ) ^ p * (∫⁻ (a : α), g a ∂μ) ^ q
tactic: have h2p : 1 < 1 / p := by
    rw [one_div]
    apply one_lt_inv hp
    linarith
state_before: case inr.inr
α✝ : Type u_1
inst✝¹ : MeasurableSpace α✝
μ✝ : Measure α✝
α : Type u_2
inst✝ : MeasurableSpace α
μ : Measure α
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
p q : ℝ
hp✝ : 0 ≤ p
hq✝ : 0 ≤ q
hpq : p + q = 1
hp : 0 < p
hq : 0 < q
h2p : 1 < 1 / p
⊢ ∫⁻ (a : α), f a ^ p * g a ^ q ∂μ ≤ (∫⁻ (a : α), f a ∂μ) ^ p * (∫⁻ (a : α), g a ∂μ) ^ q
state_after: case inr.inr
α✝ : Type u_1
inst✝¹ : MeasurableSpace α✝
μ✝ : Measure α✝
α : Type u_2
inst✝ : MeasurableSpace α
μ : Measure α
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
p q : ℝ
hp✝ : 0 ≤ p
hq✝ : 0 ≤ q
hpq : p + q = 1
hp : 0 < p
hq : 0 < q
h2p : 1 < 1 / p
h2pq : (1 / p)⁻¹ + (1 / q)⁻¹ = 1
⊢ ∫⁻ (a : α), f a ^ p * g a ^ q ∂μ ≤ (∫⁻ (a : α), f a ∂μ) ^ p * (∫⁻ (a : α), g a ∂μ) ^ q
tactic: have h2pq : (1 / p)⁻¹ + (1 / q)⁻¹ = 1 := by simp [hp.ne', hq.ne', hpq]
state_before: case inr.inr
α✝ : Type u_1
inst✝¹ : MeasurableSpace α✝
μ✝ : Measure α✝
α : Type u_2
inst✝ : MeasurableSpace α
μ : Measure α
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
p q : ℝ
hp✝ : 0 ≤ p
hq✝ : 0 ≤ q
hpq : p + q = 1
hp : 0 < p
hq : 0 < q
h2p : 1 < 1 / p
h2pq : (1 / p)⁻¹ + (1 / q)⁻¹ = 1
⊢ ∫⁻ (a : α), f a ^ p * g a ^ q ∂μ ≤ (∫⁻ (a : α), f a ∂μ) ^ p * (∫⁻ (a : α), g a ∂μ) ^ q
state_after: case inr.inr
α✝ : Type u_1
inst✝¹ : MeasurableSpace α✝
μ✝ : Measure α✝
α : Type u_2
inst✝ : MeasurableSpace α
μ : Measure α
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
p q : ℝ
hp✝ : 0 ≤ p
hq✝ : 0 ≤ q
hpq : p + q = 1
hp : 0 < p
hq : 0 < q
h2p : 1 < 1 / p
h2pq : (1 / p)⁻¹ + (1 / q)⁻¹ = 1
this :
  ∫⁻ (a : α), ((fun x => f x ^ p) * fun x => g x ^ q) a ∂μ ≤
    (∫⁻ (a : α), (f a ^ p) ^ (1 / p) ∂μ) ^ (1 / (1 / p)) * (∫⁻ (a : α), (g a ^ q) ^ (1 / q) ∂μ) ^ (1 / (1 / q))
⊢ ∫⁻ (a : α), f a ^ p * g a ^ q ∂μ ≤ (∫⁻ (a : α), f a ∂μ) ^ p * (∫⁻ (a : α), g a ∂μ) ^ q
tactic: have := ENNReal.lintegral_mul_le_Lp_mul_Lq μ ⟨h2p, h2pq⟩ (hf.pow_const p) (hg.pow_const q)
state_before: case inr.inr
α✝ : Type u_1
inst✝¹ : MeasurableSpace α✝
μ✝ : Measure α✝
α : Type u_2
inst✝ : MeasurableSpace α
μ : Measure α
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
p q : ℝ
hp✝ : 0 ≤ p
hq✝ : 0 ≤ q
hpq : p + q = 1
hp : 0 < p
hq : 0 < q
h2p : 1 < 1 / p
h2pq : (1 / p)⁻¹ + (1 / q)⁻¹ = 1
this :
  ∫⁻ (a : α), ((fun x => f x ^ p) * fun x => g x ^ q) a ∂μ ≤
    (∫⁻ (a : α), (f a ^ p) ^ (1 / p) ∂μ) ^ (1 / (1 / p)) * (∫⁻ (a : α), (g a ^ q) ^ (1 / q) ∂μ) ^ (1 / (1 / q))
⊢ ∫⁻ (a : α), f a ^ p * g a ^ q ∂μ ≤ (∫⁻ (a : α), f a ∂μ) ^ p * (∫⁻ (a : α), g a ∂μ) ^ q
state_after: no goals
tactic: simpa [← ENNReal.rpow_mul, hp.ne', hq.ne'] using this