Module: Mathlib.MeasureTheory.VectorMeasure.WithDensityVec

Goal state before:
pp: X : Type u_1
E : Type u_2
F : Type u_3
G : Type u_4
mX : MeasurableSpace X
inst✝⁶ : NormedAddCommGroup E
inst✝⁵ : NormedSpace ℝ E
inst✝⁴ : NormedAddCommGroup F
inst✝³ : NormedSpace ℝ F
inst✝² : NormedAddCommGroup G
inst✝¹ : NormedSpace ℝ G
μ : VectorMeasure X F
f : X → E
B : E →L[ℝ] F →L[ℝ] G
inst✝ : CompleteSpace G
hf : μ.Integrable f
hB : ∀ (x : E) (y : F), ‖(B x) y‖₊ = ‖B.flip y‖₊ * ‖x‖₊
s : Set X
hs : MeasurableSet s
ε : NNReal
εpos : 0 < ε
δ : NNReal := ε / 3
δpos : 0 < δ
g : X →ₛ E
hg : eLpNorm (f - ⇑g) 1 (μ.transpose B).variation ≤ ↑δ
gmem : MemLp (⇑g) 1 μ.variation
I1 : ∫⁻ (a : X) in s, ‖f a‖ₑ ∂(μ.transpose B).variation ≤ ∫⁻ (a : X) in s, ‖g a‖ₑ ∂(μ.transpose B).variation + ↑δ
I2 :
  ∫⁻ (a : X) in s, ‖g a‖ₑ ∂(μ.transpose B).variation =
    ∑ i ∈ g.range, ‖i‖ₑ * ((μ.transpose B).restrict s).variation (⇑g ⁻¹' {i})
ρ : ℝ≥0∞
ρpos : ρ > 0
hρ : ∑ i ∈ g.range, ‖i‖ₑ * ρ ≤ ↑δ
P : E → Finset (Set X)
Pg : ∀ (i : E), ∀ t ∈ P i, t ⊆ ⇑g ⁻¹' {i}
Pdisj : ∀ (i : E), (↑(P i)).PairwiseDisjoint id
Pmeas : ∀ (i : E), ∀ t ∈ P i, MeasurableSet t
hP :
  ∀ (i : E),
    ‖i‖ₑ * ((μ.transpose B).restrict s).variation (⇑g ⁻¹' {i}) ≤
      ‖i‖ₑ * (∑ p ∈ P i, ‖((μ.transpose B).restrict s) p‖ₑ + ρ)
I3 :
  ∑ i ∈ g.range, ‖i‖ₑ * ((μ.transpose B).restrict s).variation (⇑g ⁻¹' {i}) ≤
    ∑ i ∈ g.range.sigma P, ‖i.fst‖ₑ * ‖((μ.transpose B).restrict s) i.snd‖ₑ + ↑δ
I4 :
  ∑ i ∈ g.range.sigma P, ‖i.fst‖ₑ * ‖((μ.transpose B).restrict s) i.snd‖ₑ ≤
    ∑ i ∈ g.range.sigma P, ‖∫ᵛ (x : X) in i.snd, f x ∂[B; μ.restrict s]‖ₑ + ↑δ
Q : Finset (Set X) := Finset.image (fun p ↦ p.snd ∩ s) (g.range.sigma P)
⊢ (↑(g.range.sigma P)).Pairwise fun i j ↦ i.snd ∩ s = j.snd ∩ s → ‖∫ᵛ (x : X) in i.snd ∩ s, f x ∂[B; μ]‖ₑ = 0

pp: X : Type u_1
E : Type u_2
F : Type u_3
G : Type u_4
mX : MeasurableSpace X
inst✝⁶ : NormedAddCommGroup E
inst✝⁵ : NormedSpace ℝ E
inst✝⁴ : NormedAddCommGroup F
inst✝³ : NormedSpace ℝ F
inst✝² : NormedAddCommGroup G
inst✝¹ : NormedSpace ℝ G
μ : VectorMeasure X F
f : X → E
B : E →L[ℝ] F →L[ℝ] G
inst✝ : CompleteSpace G
hf : μ.Integrable f
hB : ∀ (x : E) (y : F), ‖(B x) y‖₊ = ‖B.flip y‖₊ * ‖x‖₊
s : Set X
hs : MeasurableSet s
ε : NNReal
εpos : 0 < ε
δ : NNReal := ε / 3
δpos : 0 < δ
g : X →ₛ E
hg : eLpNorm (f - ⇑g) 1 (μ.transpose B).variation ≤ ↑δ
gmem : MemLp (⇑g) 1 μ.variation
I1 : ∫⁻ (a : X) in s, ‖f a‖ₑ ∂(μ.transpose B).variation ≤ ∫⁻ (a : X) in s, ‖g a‖ₑ ∂(μ.transpose B).variation + ↑δ
I2 :
  ∫⁻ (a : X) in s, ‖g a‖ₑ ∂(μ.transpose B).variation =
    ∑ i ∈ g.range, ‖i‖ₑ * ((μ.transpose B).restrict s).variation (⇑g ⁻¹' {i})
ρ : ℝ≥0∞
ρpos : ρ > 0
hρ : ∑ i ∈ g.range, ‖i‖ₑ * ρ ≤ ↑δ
P : E → Finset (Set X)
Pg : ∀ (i : E), ∀ t ∈ P i, t ⊆ ⇑g ⁻¹' {i}
Pdisj : ∀ (i : E), (↑(P i)).PairwiseDisjoint id
Pmeas : ∀ (i : E), ∀ t ∈ P i, MeasurableSet t
hP :
  ∀ (i : E),
    ‖i‖ₑ * ((μ.transpose B).restrict s).variation (⇑g ⁻¹' {i}) ≤
      ‖i‖ₑ * (∑ p ∈ P i, ‖((μ.transpose B).restrict s) p‖ₑ + ρ)
I3 :
  ∑ i ∈ g.range, ‖i‖ₑ * ((μ.transpose B).restrict s).variation (⇑g ⁻¹' {i}) ≤
    ∑ i ∈ g.range.sigma P, ‖i.fst‖ₑ * ‖((μ.transpose B).restrict s) i.snd‖ₑ + ↑δ
I4 :
  ∑ i ∈ g.range.sigma P, ‖i.fst‖ₑ * ‖((μ.transpose B).restrict s) i.snd‖ₑ ≤
    ∑ i ∈ g.range.sigma P, ‖∫ᵛ (x : X) in i.snd, f x ∂[B; μ.restrict s]‖ₑ + ↑δ
Q : Finset (Set X) := Finset.image (fun p ↦ p.snd ∩ s) (g.range.sigma P)
⊢ ∑ i ∈ g.range.sigma P, ‖∫ᵛ (x : X) in i.snd, f x ∂[B; μ.restrict s]‖ₑ =
    ∑ i ∈ g.range.sigma P, ‖∫ᵛ (x : X) in i.snd ∩ s, f x ∂[B; μ]‖ₑ

Tactic:
· rintro ⟨i, p⟩ hi ⟨j, q⟩ hj hijpq h'ij
        simp only [Finset.coe_sigma, SimpleFunc.coe_range, mem_sigma_iff, mem_range,
          SetLike.mem_coe] at hi hj
        suffices H : Disjoint p q by
          have : Disjoint (p ∩ s) (q ∩ s) := H.mono inter_subset_left inter_subset_left
          rw [← h'ij, disjoint_self] at this
          simp [this]
        rcases eq_or_ne i j with rfl | hij
        · simp only [ne_eq, Sigma.mk.injEq, heq_eq_eq, true_and] at hijpq
          exact Pdisj i hi.2 hj.2 hijpq
        · have : Disjoint (g ⁻¹' {i}) (g ⁻¹' {j}) := by grind
          exact this.mono (Pg i p hi.2) (Pg j q hj.2)

Goal state after:
X : Type u_1
E : Type u_2
F : Type u_3
G : Type u_4
mX : MeasurableSpace X
inst✝⁶ : NormedAddCommGroup E
inst✝⁵ : NormedSpace ℝ E
inst✝⁴ : NormedAddCommGroup F
inst✝³ : NormedSpace ℝ F
inst✝² : NormedAddCommGroup G
inst✝¹ : NormedSpace ℝ G
μ : VectorMeasure X F
f : X → E
B : E →L[ℝ] F →L[ℝ] G
inst✝ : CompleteSpace G
hf : μ.Integrable f
hB : ∀ (x : E) (y : F), ‖(B x) y‖₊ = ‖B.flip y‖₊ * ‖x‖₊
s : Set X
hs : MeasurableSet s
ε : NNReal
εpos : 0 < ε
δ : NNReal := ε / 3
δpos : 0 < δ
g : X →ₛ E
hg : eLpNorm (f - ⇑g) 1 (μ.transpose B).variation ≤ ↑δ
gmem : MemLp (⇑g) 1 μ.variation
I1 : ∫⁻ (a : X) in s, ‖f a‖ₑ ∂(μ.transpose B).variation ≤ ∫⁻ (a : X) in s, ‖g a‖ₑ ∂(μ.transpose B).variation + ↑δ
I2 :
  ∫⁻ (a : X) in s, ‖g a‖ₑ ∂(μ.transpose B).variation =
    ∑ i ∈ g.range, ‖i‖ₑ * ((μ.transpose B).restrict s).variation (⇑g ⁻¹' {i})
ρ : ℝ≥0∞
ρpos : ρ > 0
hρ : ∑ i ∈ g.range, ‖i‖ₑ * ρ ≤ ↑δ
P : E → Finset (Set X)
Pg : ∀ (i : E), ∀ t ∈ P i, t ⊆ ⇑g ⁻¹' {i}
Pdisj : ∀ (i : E), (↑(P i)).PairwiseDisjoint id
Pmeas : ∀ (i : E), ∀ t ∈ P i, MeasurableSet t
hP :
  ∀ (i : E),
    ‖i‖ₑ * ((μ.transpose B).restrict s).variation (⇑g ⁻¹' {i}) ≤
      ‖i‖ₑ * (∑ p ∈ P i, ‖((μ.transpose B).restrict s) p‖ₑ + ρ)
I3 :
  ∑ i ∈ g.range, ‖i‖ₑ * ((μ.transpose B).restrict s).variation (⇑g ⁻¹' {i}) ≤
    ∑ i ∈ g.range.sigma P, ‖i.fst‖ₑ * ‖((μ.transpose B).restrict s) i.snd‖ₑ + ↑δ
I4 :
  ∑ i ∈ g.range.sigma P, ‖i.fst‖ₑ * ‖((μ.transpose B).restrict s) i.snd‖ₑ ≤
    ∑ i ∈ g.range.sigma P, ‖∫ᵛ (x : X) in i.snd, f x ∂[B; μ.restrict s]‖ₑ + ↑δ
Q : Finset (Set X) := Finset.image (fun p ↦ p.snd ∩ s) (g.range.sigma P)
⊢ ∑ i ∈ g.range.sigma P, ‖∫ᵛ (x : X) in i.snd, f x ∂[B; μ.restrict s]‖ₑ =
    ∑ i ∈ g.range.sigma P, ‖∫ᵛ (x : X) in i.snd ∩ s, f x ∂[B; μ]‖ₑ