-- Mathlib/MeasureTheory/Integral/MeanInequalities.lean
theorem lintegral_Lp_add_le {p : ℝ} {f g : α → ℝ≥0∞} (hf : AEMeasurable f μ) (hg : AEMeasurable g μ)
    (hp1 : 1 ≤ p) :
    (∫⁻ a, (f + g) a ^ p ∂μ) ^ (1 / p) ≤
      (∫⁻ a, f a ^ p ∂μ) ^ (1 / p) + (∫⁻ a, g a ^ p ∂μ) ^ (1 / p)

Proof state:
α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
p : ℝ
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
hp1 : 1 ≤ p
hp_pos : 0 < p
hf_top : ¬∫⁻ (a : α), f a ^ p ∂μ = ⊤
hg_top : ¬∫⁻ (a : α), g a ^ p ∂μ = ⊤
h1 : ¬p = 1
⊢ p ≠ 1

Tactic:
exact h1

Result:
no goals

Proof state:
case neg
α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
p : ℝ
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
hp1 : 1 ≤ p
hp_pos : 0 < p
hf_top : ¬∫⁻ (a : α), f a ^ p ∂μ = ⊤
⊢ (∫⁻ (a : α), (f + g) a ^ p ∂μ) ^ (1 / p) ≤ (∫⁻ (a : α), f a ^ p ∂μ) ^ (1 / p) + (∫⁻ (a : α), g a ^ p ∂μ) ^ (1 / p)

Tactic:
by_cases hg_top : ∫⁻ a, g a ^ p ∂μ = ⊤

Result:
case pos
α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
p : ℝ
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
hp1 : 1 ≤ p
hp_pos : 0 < p
hf_top : ¬∫⁻ (a : α), f a ^ p ∂μ = ⊤
hg_top : ∫⁻ (a : α), g a ^ p ∂μ = ⊤
⊢ (∫⁻ (a : α), (f + g) a ^ p ∂μ) ^ (1 / p) ≤ (∫⁻ (a : α), f a ^ p ∂μ) ^ (1 / p) + (∫⁻ (a : α), g a ^ p ∂μ) ^ (1 / p)

case neg
α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
p : ℝ
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
hp1 : 1 ≤ p
hp_pos : 0 < p
hf_top : ¬∫⁻ (a : α), f a ^ p ∂μ = ⊤
hg_top : ¬∫⁻ (a : α), g a ^ p ∂μ = ⊤
⊢ (∫⁻ (a : α), (f + g) a ^ p ∂μ) ^ (1 / p) ≤ (∫⁻ (a : α), f a ^ p ∂μ) ^ (1 / p) + (∫⁻ (a : α), g a ^ p ∂μ) ^ (1 / p)

Proof state:
α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
p : ℝ
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
hp1 : 1 ≤ p
hp_pos : 0 < p
hf_top : ¬∫⁻ (a : α), f a ^ p ∂μ = ⊤
hg_top : ¬∫⁻ (a : α), g a ^ p ∂μ = ⊤
h1 : ¬p = 1
hp1_lt : 1 < p
hpq : p.IsConjExponent p.conjExponent
h0 : ¬∫⁻ (a : α), (f + g) a ^ p ∂μ = 0
⊢ ∫⁻ (a : α), (f + g) a ^ p ∂μ ≠ ⊤

Tactic:
rw [← Ne] at hf_top hg_top

Result:
α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
p : ℝ
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
hp1 : 1 ≤ p
hp_pos : 0 < p
hf_top : ∫⁻ (a : α), f a ^ p ∂μ ≠ ⊤
hg_top : ∫⁻ (a : α), g a ^ p ∂μ ≠ ⊤
h1 : ¬p = 1
hp1_lt : 1 < p
hpq : p.IsConjExponent p.conjExponent
h0 : ¬∫⁻ (a : α), (f + g) a ^ p ∂μ = 0
⊢ ∫⁻ (a : α), (f + g) a ^ p ∂μ ≠ ⊤

Proof state:
case neg
α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
p : ℝ
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
hp1 : 1 ≤ p
hp_pos : 0 < p
hf_top : ¬∫⁻ (a : α), f a ^ p ∂μ = ⊤
hg_top : ¬∫⁻ (a : α), g a ^ p ∂μ = ⊤
h1 : ¬p = 1
hp1_lt : 1 < p
hpq : p.IsConjExponent p.conjExponent
h0 : ¬∫⁻ (a : α), (f + g) a ^ p ∂μ = 0
htop : ∫⁻ (a : α), (f + g) a ^ p ∂μ ≠ ⊤
⊢ (∫⁻ (a : α), (f + g) a ^ p ∂μ) ^ (1 / p) ≤ (∫⁻ (a : α), f a ^ p ∂μ) ^ (1 / p) + (∫⁻ (a : α), g a ^ p ∂μ) ^ (1 / p)

Tactic:
exact lintegral_Lp_add_le_aux hpq hf hf_top hg hg_top h0 htop

Result:
no goals

Proof state:
case pos
α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
p : ℝ
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
hp1 : 1 ≤ p
hp_pos : 0 < p
hf_top : ∫⁻ (a : α), f a ^ p ∂μ = ⊤
⊢ (∫⁻ (a : α), (f + g) a ^ p ∂μ) ^ (1 / p) ≤ (∫⁻ (a : α), f a ^ p ∂μ) ^ (1 / p) + (∫⁻ (a : α), g a ^ p ∂μ) ^ (1 / p)

Tactic:
simp [hf_top, hp_pos]

Result:
no goals

Proof state:
case neg
α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
p : ℝ
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
hp1 : 1 ≤ p
hp_pos : 0 < p
hf_top : ¬∫⁻ (a : α), f a ^ p ∂μ = ⊤
hg_top : ¬∫⁻ (a : α), g a ^ p ∂μ = ⊤
h1 : ¬p = 1
⊢ (∫⁻ (a : α), (f + g) a ^ p ∂μ) ^ (1 / p) ≤ (∫⁻ (a : α), f a ^ p ∂μ) ^ (1 / p) + (∫⁻ (a : α), g a ^ p ∂μ) ^ (1 / p)

Tactic:
have hp1_lt : 1 < p := by
  refine lt_of_le_of_ne hp1 ?_
  symm
  exact h1

Result:
case neg
α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
p : ℝ
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
hp1 : 1 ≤ p
hp_pos : 0 < p
hf_top : ¬∫⁻ (a : α), f a ^ p ∂μ = ⊤
hg_top : ¬∫⁻ (a : α), g a ^ p ∂μ = ⊤
h1 : ¬p = 1
hp1_lt : 1 < p
⊢ (∫⁻ (a : α), (f + g) a ^ p ∂μ) ^ (1 / p) ≤ (∫⁻ (a : α), f a ^ p ∂μ) ^ (1 / p) + (∫⁻ (a : α), g a ^ p ∂μ) ^ (1 / p)

Proof state:
case pos
α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
p : ℝ
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
hp1 : 1 ≤ p
hp_pos : 0 < p
hf_top : ¬∫⁻ (a : α), f a ^ p ∂μ = ⊤
hg_top : ∫⁻ (a : α), g a ^ p ∂μ = ⊤
⊢ (∫⁻ (a : α), (f + g) a ^ p ∂μ) ^ (1 / p) ≤ (∫⁻ (a : α), f a ^ p ∂μ) ^ (1 / p) + (∫⁻ (a : α), g a ^ p ∂μ) ^ (1 / p)

Tactic:
simp [hg_top, hp_pos]

Result:
no goals

Proof state:
α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
p : ℝ
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
hp1 : 1 ≤ p
hp_pos : 0 < p
⊢ (∫⁻ (a : α), (f + g) a ^ p ∂μ) ^ (1 / p) ≤ (∫⁻ (a : α), f a ^ p ∂μ) ^ (1 / p) + (∫⁻ (a : α), g a ^ p ∂μ) ^ (1 / p)

Tactic:
by_cases hf_top : ∫⁻ a, f a ^ p ∂μ = ⊤

Result:
case pos
α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
p : ℝ
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
hp1 : 1 ≤ p
hp_pos : 0 < p
hf_top : ∫⁻ (a : α), f a ^ p ∂μ = ⊤
⊢ (∫⁻ (a : α), (f + g) a ^ p ∂μ) ^ (1 / p) ≤ (∫⁻ (a : α), f a ^ p ∂μ) ^ (1 / p) + (∫⁻ (a : α), g a ^ p ∂μ) ^ (1 / p)

case neg
α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
p : ℝ
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
hp1 : 1 ≤ p
hp_pos : 0 < p
hf_top : ¬∫⁻ (a : α), f a ^ p ∂μ = ⊤
⊢ (∫⁻ (a : α), (f + g) a ^ p ∂μ) ^ (1 / p) ≤ (∫⁻ (a : α), f a ^ p ∂μ) ^ (1 / p) + (∫⁻ (a : α), g a ^ p ∂μ) ^ (1 / p)

Proof state:
case neg
α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
p : ℝ
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
hp1 : 1 ≤ p
hp_pos : 0 < p
hf_top : ¬∫⁻ (a : α), f a ^ p ∂μ = ⊤
hg_top : ¬∫⁻ (a : α), g a ^ p ∂μ = ⊤
h1 : ¬p = 1
hp1_lt : 1 < p
hpq : p.IsConjExponent p.conjExponent
h0 : ¬∫⁻ (a : α), (f + g) a ^ p ∂μ = 0
⊢ (∫⁻ (a : α), (f + g) a ^ p ∂μ) ^ (1 / p) ≤ (∫⁻ (a : α), f a ^ p ∂μ) ^ (1 / p) + (∫⁻ (a : α), g a ^ p ∂μ) ^ (1 / p)

Tactic:
have htop : (∫⁻ a, (f + g) a ^ p ∂μ) ≠ ⊤ := by
  rw [← Ne] at hf_top hg_top
  rw [← lt_top_iff_ne_top] at hf_top hg_top ⊢
  exact lintegral_rpow_add_lt_top_of_lintegral_rpow_lt_top hf hf_top hg_top hp1

Result:
case neg
α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
p : ℝ
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
hp1 : 1 ≤ p
hp_pos : 0 < p
hf_top : ¬∫⁻ (a : α), f a ^ p ∂μ = ⊤
hg_top : ¬∫⁻ (a : α), g a ^ p ∂μ = ⊤
h1 : ¬p = 1
hp1_lt : 1 < p
hpq : p.IsConjExponent p.conjExponent
h0 : ¬∫⁻ (a : α), (f + g) a ^ p ∂μ = 0
htop : ∫⁻ (a : α), (f + g) a ^ p ∂μ ≠ ⊤
⊢ (∫⁻ (a : α), (f + g) a ^ p ∂μ) ^ (1 / p) ≤ (∫⁻ (a : α), f a ^ p ∂μ) ^ (1 / p) + (∫⁻ (a : α), g a ^ p ∂μ) ^ (1 / p)

Proof state:
α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
p : ℝ
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
hp1 : 1 ≤ p
hp_pos : 0 < p
hf_top : ¬∫⁻ (a : α), f a ^ p ∂μ = ⊤
hg_top : ¬∫⁻ (a : α), g a ^ p ∂μ = ⊤
h1 : ¬p = 1
⊢ 1 < p

Tactic:
refine lt_of_le_of_ne hp1 ?_

Result:
α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
p : ℝ
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hg : AEMeasurable g μ
hp1 : 1 ≤ p
hp_pos : 0 < p
hf_top : ¬∫⁻ (a : α), f a ^ p ∂μ = ⊤
hg_top : ¬∫⁻ (a : α), g a ^ p ∂μ = ⊤
h1 : ¬p = 1
⊢ 1 ≠ p