-- Mathlib/Analysis/BoxIntegral/Partition/Filter.lean
theorem MemBaseSet.filter (hπ : l.MemBaseSet I c r π) (p : Box ι → Prop) :
    l.MemBaseSet I c r (π.filter p)

Proof state:
case intro.intro.refine_2
ι : Type u_1
inst✝ : Fintype ι
I : Box ι
c : ℝ≥0
l : IntegrationParams
π : TaggedPrepartition I
r : (ι → ℝ) → ↑(Set.Ioi 0)
hπ : l.MemBaseSet I c r π
p : Box ι → Prop
hD : l.bDistortion = true
π₁ : Prepartition I
hπ₁U : π₁.iUnion = ↑I \ π.iUnion
hc : π₁.distortion ≤ c
π₂ : TaggedPrepartition I := π.filter fun J => ¬p J
this✝ : Disjoint π₁.iUnion π₂.iUnion
this : (π.filter fun J => ¬p J).distortion ≤ c
⊢ (π₁.disjUnion π₂.toPrepartition this✝).distortion ≤ c

Tactic:
simpa [hc]

Result:
no goals

Proof state:
case intro.intro.refine_1.h.mpr.intro
ι : Type u_1
inst✝ : Fintype ι
I : Box ι
c : ℝ≥0
l : IntegrationParams
π : TaggedPrepartition I
r : (ι → ℝ) → ↑(Set.Ioi 0)
hπ : l.MemBaseSet I c r π
p : Box ι → Prop
hD : l.bDistortion = true
π₁ : Prepartition I
hπ₁U : π₁.iUnion = ↑I \ π.iUnion
hc : π₁.distortion ≤ c
π₂ : TaggedPrepartition I := π.filter fun J => ¬p J
this : Disjoint π₁.iUnion π₂.iUnion
h : (π.filter p).iUnion ⊆ π.iUnion
x : ι → ℝ
hxI : x ∈ ↑I
hxp : x ∉ (π.filter p).iUnion
⊢ x ∈ ↑I \ π.iUnion ∪ π.iUnion \ (π.filter p).iUnion

Tactic:
by_cases hxπ : x ∈ π.iUnion

Result:
case pos
ι : Type u_1
inst✝ : Fintype ι
I : Box ι
c : ℝ≥0
l : IntegrationParams
π : TaggedPrepartition I
r : (ι → ℝ) → ↑(Set.Ioi 0)
hπ : l.MemBaseSet I c r π
p : Box ι → Prop
hD : l.bDistortion = true
π₁ : Prepartition I
hπ₁U : π₁.iUnion = ↑I \ π.iUnion
hc : π₁.distortion ≤ c
π₂ : TaggedPrepartition I := π.filter fun J => ¬p J
this : Disjoint π₁.iUnion π₂.iUnion
h : (π.filter p).iUnion ⊆ π.iUnion
x : ι → ℝ
hxI : x ∈ ↑I
hxp : x ∉ (π.filter p).iUnion
hxπ : x ∈ π.iUnion
⊢ x ∈ ↑I \ π.iUnion ∪ π.iUnion \ (π.filter p).iUnion

case neg
ι : Type u_1
inst✝ : Fintype ι
I : Box ι
c : ℝ≥0
l : IntegrationParams
π : TaggedPrepartition I
r : (ι → ℝ) → ↑(Set.Ioi 0)
hπ : l.MemBaseSet I c r π
p : Box ι → Prop
hD : l.bDistortion = true
π₁ : Prepartition I
hπ₁U : π₁.iUnion = ↑I \ π.iUnion
hc : π₁.distortion ≤ c
π₂ : TaggedPrepartition I := π.filter fun J => ¬p J
this : Disjoint π₁.iUnion π₂.iUnion
h : (π.filter p).iUnion ⊆ π.iUnion
x : ι → ℝ
hxI : x ∈ ↑I
hxp : x ∉ (π.filter p).iUnion
hxπ : x ∉ π.iUnion
⊢ x ∈ ↑I \ π.iUnion ∪ π.iUnion \ (π.filter p).iUnion

Proof state:
case intro.intro.refine_1.h
ι : Type u_1
inst✝ : Fintype ι
I : Box ι
c : ℝ≥0
l : IntegrationParams
π : TaggedPrepartition I
r : (ι → ℝ) → ↑(Set.Ioi 0)
hπ : l.MemBaseSet I c r π
p : Box ι → Prop
hD : l.bDistortion = true
π₁ : Prepartition I
hπ₁U : π₁.iUnion = ↑I \ π.iUnion
hc : π₁.distortion ≤ c
π₂ : TaggedPrepartition I := π.filter fun J => ¬p J
this : Disjoint π₁.iUnion π₂.iUnion
h : (π.filter p).iUnion ⊆ π.iUnion
x : ι → ℝ
⊢ x ∈ ↑I \ π.iUnion ∪ π.iUnion \ (π.filter p).iUnion ↔ x ∈ ↑I \ (π.filter p).iUnion

Tactic:
fconstructor

Result:
case intro.intro.refine_1.h.mp
ι : Type u_1
inst✝ : Fintype ι
I : Box ι
c : ℝ≥0
l : IntegrationParams
π : TaggedPrepartition I
r : (ι → ℝ) → ↑(Set.Ioi 0)
hπ : l.MemBaseSet I c r π
p : Box ι → Prop
hD : l.bDistortion = true
π₁ : Prepartition I
hπ₁U : π₁.iUnion = ↑I \ π.iUnion
hc : π₁.distortion ≤ c
π₂ : TaggedPrepartition I := π.filter fun J => ¬p J
this : Disjoint π₁.iUnion π₂.iUnion
h : (π.filter p).iUnion ⊆ π.iUnion
x : ι → ℝ
⊢ x ∈ ↑I \ π.iUnion ∪ π.iUnion \ (π.filter p).iUnion → x ∈ ↑I \ (π.filter p).iUnion

case intro.intro.refine_1.h.mpr
ι : Type u_1
inst✝ : Fintype ι
I : Box ι
c : ℝ≥0
l : IntegrationParams
π : TaggedPrepartition I
r : (ι → ℝ) → ↑(Set.Ioi 0)
hπ : l.MemBaseSet I c r π
p : Box ι → Prop
hD : l.bDistortion = true
π₁ : Prepartition I
hπ₁U : π₁.iUnion = ↑I \ π.iUnion
hc : π₁.distortion ≤ c
π₂ : TaggedPrepartition I := π.filter fun J => ¬p J
this : Disjoint π₁.iUnion π₂.iUnion
h : (π.filter p).iUnion ⊆ π.iUnion
x : ι → ℝ
⊢ x ∈ ↑I \ (π.filter p).iUnion → x ∈ ↑I \ π.iUnion ∪ π.iUnion \ (π.filter p).iUnion

Proof state:
case pos
ι : Type u_1
inst✝ : Fintype ι
I : Box ι
c : ℝ≥0
l : IntegrationParams
π : TaggedPrepartition I
r : (ι → ℝ) → ↑(Set.Ioi 0)
hπ : l.MemBaseSet I c r π
p : Box ι → Prop
hD : l.bDistortion = true
π₁ : Prepartition I
hπ₁U : π₁.iUnion = ↑I \ π.iUnion
hc : π₁.distortion ≤ c
π₂ : TaggedPrepartition I := π.filter fun J => ¬p J
this : Disjoint π₁.iUnion π₂.iUnion
h : (π.filter p).iUnion ⊆ π.iUnion
x : ι → ℝ
hxI : x ∈ ↑I
hxp : x ∉ (π.filter p).iUnion
hxπ : x ∈ π.iUnion
⊢ x ∈ ↑I \ π.iUnion ∪ π.iUnion \ (π.filter p).iUnion

case neg
ι : Type u_1
inst✝ : Fintype ι
I : Box ι
c : ℝ≥0
l : IntegrationParams
π : TaggedPrepartition I
r : (ι → ℝ) → ↑(Set.Ioi 0)
hπ : l.MemBaseSet I c r π
p : Box ι → Prop
hD : l.bDistortion = true
π₁ : Prepartition I
hπ₁U : π₁.iUnion = ↑I \ π.iUnion
hc : π₁.distortion ≤ c
π₂ : TaggedPrepartition I := π.filter fun J => ¬p J
this : Disjoint π₁.iUnion π₂.iUnion
h : (π.filter p).iUnion ⊆ π.iUnion
x : ι → ℝ
hxI : x ∈ ↑I
hxp : x ∉ (π.filter p).iUnion
hxπ : x ∉ π.iUnion
⊢ x ∈ ↑I \ π.iUnion ∪ π.iUnion \ (π.filter p).iUnion

Tactic:
exacts [Or.inr ⟨hxπ, hxp⟩, Or.inl ⟨hxI, hxπ⟩]

Result:
no goals

Proof state:
ι : Type u_1
inst✝ : Fintype ι
I : Box ι
c : ℝ≥0
l : IntegrationParams
π : TaggedPrepartition I
r : (ι → ℝ) → ↑(Set.Ioi 0)
hπ : l.MemBaseSet I c r π
p : Box ι → Prop
⊢ l.MemBaseSet I c r (π.filter p)

Tactic:
refine ⟨fun J hJ => hπ.1 J (π.mem_filter.1 hJ).1, fun hH J hJ => hπ.2 hH J (π.mem_filter.1 hJ).1,
  fun hD => (distortion_filter_le _ _).trans (hπ.3 hD), fun hD => ?_⟩

Result:
ι : Type u_1
inst✝ : Fintype ι
I : Box ι
c : ℝ≥0
l : IntegrationParams
π : TaggedPrepartition I
r : (ι → ℝ) → ↑(Set.Ioi 0)
hπ : l.MemBaseSet I c r π
p : Box ι → Prop
hD : l.bDistortion = true
⊢ ∃ π', π'.iUnion = ↑I \ (π.filter p).iUnion ∧ π'.distortion ≤ c

Proof state:
case intro.intro.refine_1.h.mp.inl.intro
ι : Type u_1
inst✝ : Fintype ι
I : Box ι
c : ℝ≥0
l : IntegrationParams
π : TaggedPrepartition I
r : (ι → ℝ) → ↑(Set.Ioi 0)
hπ : l.MemBaseSet I c r π
p : Box ι → Prop
hD : l.bDistortion = true
π₁ : Prepartition I
hπ₁U : π₁.iUnion = ↑I \ π.iUnion
hc : π₁.distortion ≤ c
π₂ : TaggedPrepartition I := π.filter fun J => ¬p J
this : Disjoint π₁.iUnion π₂.iUnion
h : (π.filter p).iUnion ⊆ π.iUnion
x : ι → ℝ
hxI : x ∈ ↑I
hxπ : x ∉ π.iUnion
⊢ x ∈ ↑I \ (π.filter p).iUnion

case intro.intro.refine_1.h.mp.inr.intro
ι : Type u_1
inst✝ : Fintype ι
I : Box ι
c : ℝ≥0
l : IntegrationParams
π : TaggedPrepartition I
r : (ι → ℝ) → ↑(Set.Ioi 0)
hπ : l.MemBaseSet I c r π
p : Box ι → Prop
hD : l.bDistortion = true
π₁ : Prepartition I
hπ₁U : π₁.iUnion = ↑I \ π.iUnion
hc : π₁.distortion ≤ c
π₂ : TaggedPrepartition I := π.filter fun J => ¬p J
this : Disjoint π₁.iUnion π₂.iUnion
h : (π.filter p).iUnion ⊆ π.iUnion
x : ι → ℝ
hxπ : x ∈ π.iUnion
hxp : x ∉ (π.filter p).iUnion
⊢ x ∈ ↑I \ (π.filter p).iUnion

Tactic:
exacts [⟨hxI, mt (@h x) hxπ⟩, ⟨π.iUnion_subset hxπ, hxp⟩]

Result:
no goals

Proof state:
ι : Type u_1
inst✝ : Fintype ι
I : Box ι
c : ℝ≥0
l : IntegrationParams
π : TaggedPrepartition I
r : (ι → ℝ) → ↑(Set.Ioi 0)
hπ : l.MemBaseSet I c r π
p : Box ι → Prop
hD : l.bDistortion = true
π₁ : Prepartition I
hπ₁U : π₁.iUnion = ↑I \ π.iUnion
hc : π₁.distortion ≤ c
π₂ : TaggedPrepartition I := π.filter fun J => ¬p J
this✝ : Disjoint π₁.iUnion π₂.iUnion
this : ↑I \ π.iUnion ∪ π.iUnion \ (π.filter p).iUnion = ↑I \ (π.filter p).iUnion
⊢ (π₁.disjUnion π₂.toPrepartition this✝).iUnion = ↑I \ (π.filter p).iUnion

Tactic:
simp [π₂, *]

Result:
no goals