Theorem: MeasureTheory.ae_nonneg_of_forall_setIntegral_nonneg
File: Mathlib/MeasureTheory/Function/AEEqOfIntegral.lean

Proof steps:
state_before: α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
μ : Measure α
s t : Set α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
p : ℝ≥0∞
f : α → ℝ
hf : Integrable f μ
hf_zero : ∀ (s : Set α), MeasurableSet s → μ s < ⊤ → 0 ≤ ∫ (x : α) in s, f x ∂μ
⊢ 0 ≤ᶠ[ae μ] f
state_after: α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
μ : Measure α
s t : Set α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
p : ℝ≥0∞
f : α → ℝ
hf : Integrable f μ
hf_zero : ∀ (s : Set α), MeasurableSet s → μ s < ⊤ → 0 ≤ ∫ (x : α) in s, f x ∂μ
⊢ ∀ᵐ (x : α) ∂μ, 0 ≤ f x
tactic: simp_rw [EventuallyLE, Pi.zero_apply]
state_before: α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
μ : Measure α
s t : Set α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
p : ℝ≥0∞
f : α → ℝ
hf : Integrable f μ
hf_zero : ∀ (s : Set α), MeasurableSet s → μ s < ⊤ → 0 ≤ ∫ (x : α) in s, f x ∂μ
⊢ ∀ᵐ (x : α) ∂μ, 0 ≤ f x
state_after: α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
μ : Measure α
s t : Set α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
p : ℝ≥0∞
f : α → ℝ
hf : Integrable f μ
hf_zero : ∀ (s : Set α), MeasurableSet s → μ s < ⊤ → 0 ≤ ∫ (x : α) in s, f x ∂μ
⊢ ∀ b < 0, μ {x | f x ≤ b} = 0
tactic: rw [ae_const_le_iff_forall_lt_measure_zero]
state_before: α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
μ : Measure α
s t : Set α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
p : ℝ≥0∞
f : α → ℝ
hf : Integrable f μ
hf_zero : ∀ (s : Set α), MeasurableSet s → μ s < ⊤ → 0 ≤ ∫ (x : α) in s, f x ∂μ
⊢ ∀ b < 0, μ {x | f x ≤ b} = 0
state_after: α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
μ : Measure α
s t : Set α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
p : ℝ≥0∞
f : α → ℝ
hf : Integrable f μ
hf_zero : ∀ (s : Set α), MeasurableSet s → μ s < ⊤ → 0 ≤ ∫ (x : α) in s, f x ∂μ
b : ℝ
hb_neg : b < 0
⊢ μ {x | f x ≤ b} = 0
tactic: intro b hb_neg
state_before: α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
μ : Measure α
s t : Set α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
p : ℝ≥0∞
f : α → ℝ
hf : Integrable f μ
hf_zero : ∀ (s : Set α), MeasurableSet s → μ s < ⊤ → 0 ≤ ∫ (x : α) in s, f x ∂μ
b : ℝ
hb_neg : b < 0
⊢ μ {x | f x ≤ b} = 0
state_after: α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
μ : Measure α
s✝ t : Set α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
p : ℝ≥0∞
f : α → ℝ
hf : Integrable f μ
hf_zero : ∀ (s : Set α), MeasurableSet s → μ s < ⊤ → 0 ≤ ∫ (x : α) in s, f x ∂μ
b : ℝ
hb_neg : b < 0
s : Set α := {x | f x ≤ b}
⊢ μ {x | f x ≤ b} = 0
tactic: let s := {x | f x ≤ b}
state_before: α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
μ : Measure α
s✝ t : Set α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
p : ℝ≥0∞
f : α → ℝ
hf : Integrable f μ
hf_zero : ∀ (s : Set α), MeasurableSet s → μ s < ⊤ → 0 ≤ ∫ (x : α) in s, f x ∂μ
b : ℝ
hb_neg : b < 0
s : Set α := {x | f x ≤ b}
⊢ μ {x | f x ≤ b} = 0
state_after: α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
μ : Measure α
s✝ t : Set α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
p : ℝ≥0∞
f : α → ℝ
hf : Integrable f μ
hf_zero : ∀ (s : Set α), MeasurableSet s → μ s < ⊤ → 0 ≤ ∫ (x : α) in s, f x ∂μ
b : ℝ
hb_neg : b < 0
s : Set α := {x | f x ≤ b}
hs : NullMeasurableSet s μ
⊢ μ {x | f x ≤ b} = 0
tactic: have hs : NullMeasurableSet s μ := nullMeasurableSet_le hf.1.aemeasurable aemeasurable_const
state_before: α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
μ : Measure α
s✝ t : Set α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
p : ℝ≥0∞
f : α → ℝ
hf : Integrable f μ
hf_zero : ∀ (s : Set α), MeasurableSet s → μ s < ⊤ → 0 ≤ ∫ (x : α) in s, f x ∂μ
b : ℝ
hb_neg : b < 0
s : Set α := {x | f x ≤ b}
hs : NullMeasurableSet s μ
⊢ μ {x | f x ≤ b} = 0
state_after: α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
μ : Measure α
s✝ t : Set α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
p : ℝ≥0∞
f : α → ℝ
hf : Integrable f μ
hf_zero : ∀ (s : Set α), MeasurableSet s → μ s < ⊤ → 0 ≤ ∫ (x : α) in s, f x ∂μ
b : ℝ
hb_neg : b < 0
s : Set α := {x | f x ≤ b}
hs : NullMeasurableSet s μ
mus : μ s < ⊤
⊢ μ {x | f x ≤ b} = 0
tactic: have mus : μ s < ∞ := Integrable.measure_le_lt_top hf hb_neg
state_before: α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
μ : Measure α
s✝ t : Set α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
p : ℝ≥0∞
f : α → ℝ
hf : Integrable f μ
hf_zero : ∀ (s : Set α), MeasurableSet s → μ s < ⊤ → 0 ≤ ∫ (x : α) in s, f x ∂μ
b : ℝ
hb_neg : b < 0
s : Set α := {x | f x ≤ b}
hs : NullMeasurableSet s μ
mus : μ s < ⊤
⊢ μ {x | f x ≤ b} = 0
state_after: α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
μ : Measure α
s✝ t : Set α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
p : ℝ≥0∞
f : α → ℝ
hf : Integrable f μ
hf_zero : ∀ (s : Set α), MeasurableSet s → μ s < ⊤ → 0 ≤ ∫ (x : α) in s, f x ∂μ
b : ℝ
hb_neg : b < 0
s : Set α := {x | f x ≤ b}
hs : NullMeasurableSet s μ
mus : μ s < ⊤
h_int_gt : ∫ (x : α) in s, f x ∂μ ≤ b * (μ s).toReal
⊢ μ {x | f x ≤ b} = 0
tactic: have h_int_gt : (∫ x in s, f x ∂μ) ≤ b * (μ s).toReal := by
    have h_const_le : (∫ x in s, f x ∂μ) ≤ ∫ _ in s, b ∂μ := by
      refine setIntegral_mono_ae_restrict hf.integrableOn (integrableOn_const.mpr (Or.inr mus)) ?_
      rw [EventuallyLE, ae_restrict_iff₀ (hs.mono μ.restrict_le_self)]
      exact eventually_of_forall fun x hxs => hxs
    rwa [setIntegral_const, smul_eq_mul, mul_comm] at h_const_le
state_before: α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
μ : Measure α
s✝ t : Set α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
p : ℝ≥0∞
f : α → ℝ
hf : Integrable f μ
hf_zero : ∀ (s : Set α), MeasurableSet s → μ s < ⊤ → 0 ≤ ∫ (x : α) in s, f x ∂μ
b : ℝ
hb_neg : b < 0
s : Set α := {x | f x ≤ b}
hs : NullMeasurableSet s μ
mus : μ s < ⊤
h_int_gt : ∫ (x : α) in s, f x ∂μ ≤ b * (μ s).toReal
⊢ μ {x | f x ≤ b} = 0
state_after: α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
μ : Measure α
s✝ t : Set α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
p : ℝ≥0∞
f : α → ℝ
hf : Integrable f μ
hf_zero : ∀ (s : Set α), MeasurableSet s → μ s < ⊤ → 0 ≤ ∫ (x : α) in s, f x ∂μ
b : ℝ
hb_neg : b < 0
s : Set α := {x | f x ≤ b}
hs : NullMeasurableSet s μ
mus : μ s < ⊤
H : μ {x | f x ≤ b} ≠ 0
⊢ b * (μ s).toReal < ∫ (x : α) in s, f x ∂μ
tactic: contrapose! h_int_gt with H
state_before: α : Type u_1
E : Type u_2
m m0 : MeasurableSpace α
μ : Measure α
s✝ t : Set α
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
p : ℝ≥0∞
f : α → ℝ
hf : Integrable f μ
hf_zero : ∀ (s : Set α), MeasurableSet s → μ s < ⊤ → 0 ≤ ∫ (x : α) in s, f x ∂μ
b : ℝ
hb_neg : b < 0
s : Set α := {x | f x ≤ b}
hs : NullMeasurableSet s μ
mus : μ s < ⊤
H : μ {x | f x ≤ b} ≠ 0
⊢ b * (μ s).toReal < ∫ (x : α) in s, f x ∂μ
state_after: no goals
tactic: calc
    b * (μ s).toReal < 0 := mul_neg_of_neg_of_pos hb_neg <| ENNReal.toReal_pos H mus.ne
    _ ≤ ∫ x in s, f x ∂μ := by
      rw [← μ.restrict_toMeasurable mus.ne]
      exact hf_zero _ (measurableSet_toMeasurable ..) (by rwa [measure_toMeasurable])