Theorem: BoxIntegral.Prepartition.injOn_setOf_mem_Icc_setOf_lower_eq
File: Mathlib/Analysis/BoxIntegral/Partition/Basic.lean

Proof steps:
state_before: ι : Type u_1
I J J₁ J₂ : Box ι
π π₁ π₂ : Prepartition I
x✝ x : ι → ℝ
⊢ InjOn (fun J => {i | J.lower i = x i}) {J | J ∈ π ∧ x ∈ Box.Icc J}
state_after: case intro.intro
ι : Type u_1
I J J₁✝ J₂✝ : Box ι
π π₁ π₂ : Prepartition I
x✝ x : ι → ℝ
J₁ : Box ι
h₁ : J₁ ∈ π
hx₁ : x ∈ Box.Icc J₁
J₂ : Box ι
h₂ : J₂ ∈ π
hx₂ : x ∈ Box.Icc J₂
H : {i | J₁.lower i = x i} = {i | J₂.lower i = x i}
⊢ J₁ = J₂
tactic: rintro J₁ ⟨h₁, hx₁⟩ J₂ ⟨h₂, hx₂⟩ (H : { i | J₁.lower i = x i } = { i | J₂.lower i = x i })
state_before: case intro.intro
ι : Type u_1
I J J₁✝ J₂✝ : Box ι
π π₁ π₂ : Prepartition I
x✝ x : ι → ℝ
J₁ : Box ι
h₁ : J₁ ∈ π
hx₁ : x ∈ Box.Icc J₁
J₂ : Box ι
h₂ : J₂ ∈ π
hx₂ : x ∈ Box.Icc J₂
H : {i | J₁.lower i = x i} = {i | J₂.lower i = x i}
⊢ J₁ = J₂
state_after: case intro.intro
ι : Type u_1
I J J₁✝ J₂✝ : Box ι
π π₁ π₂ : Prepartition I
x✝ x : ι → ℝ
J₁ : Box ι
h₁ : J₁ ∈ π
hx₁ : x ∈ Box.Icc J₁
J₂ : Box ι
h₂ : J₂ ∈ π
hx₂ : x ∈ Box.Icc J₂
H : {i | J₁.lower i = x i} = {i | J₂.lower i = x i}
⊢ ∀ (i : ι), (Set.Ioc (J₁.lower i) (J₁.upper i) ∩ Set.Ioc (J₂.lower i) (J₂.upper i)).Nonempty
tactic: suffices ∀ i, (Ioc (J₁.lower i) (J₁.upper i) ∩ Ioc (J₂.lower i) (J₂.upper i)).Nonempty by
    choose y hy₁ hy₂ using this
    exact π.eq_of_mem_of_mem h₁ h₂ hy₁ hy₂
state_before: case intro.intro
ι : Type u_1
I J J₁✝ J₂✝ : Box ι
π π₁ π₂ : Prepartition I
x✝ x : ι → ℝ
J₁ : Box ι
h₁ : J₁ ∈ π
hx₁ : x ∈ Box.Icc J₁
J₂ : Box ι
h₂ : J₂ ∈ π
hx₂ : x ∈ Box.Icc J₂
H : {i | J₁.lower i = x i} = {i | J₂.lower i = x i}
⊢ ∀ (i : ι), (Set.Ioc (J₁.lower i) (J₁.upper i) ∩ Set.Ioc (J₂.lower i) (J₂.upper i)).Nonempty
state_after: case intro.intro
ι : Type u_1
I J J₁✝ J₂✝ : Box ι
π π₁ π₂ : Prepartition I
x✝ x : ι → ℝ
J₁ : Box ι
h₁ : J₁ ∈ π
hx₁ : x ∈ Box.Icc J₁
J₂ : Box ι
h₂ : J₂ ∈ π
hx₂ : x ∈ Box.Icc J₂
H : {i | J₁.lower i = x i} = {i | J₂.lower i = x i}
i : ι
⊢ (Set.Ioc (J₁.lower i) (J₁.upper i) ∩ Set.Ioc (J₂.lower i) (J₂.upper i)).Nonempty
tactic: intro i
state_before: case intro.intro
ι : Type u_1
I J J₁✝ J₂✝ : Box ι
π π₁ π₂ : Prepartition I
x✝ x : ι → ℝ
J₁ : Box ι
h₁ : J₁ ∈ π
hx₁ : x ∈ Box.Icc J₁
J₂ : Box ι
h₂ : J₂ ∈ π
hx₂ : x ∈ Box.Icc J₂
H : {i | J₁.lower i = x i} = {i | J₂.lower i = x i}
i : ι
⊢ (Set.Ioc (J₁.lower i) (J₁.upper i) ∩ Set.Ioc (J₂.lower i) (J₂.upper i)).Nonempty
state_after: case intro.intro
ι : Type u_1
I J J₁✝ J₂✝ : Box ι
π π₁ π₂ : Prepartition I
x✝ x : ι → ℝ
J₁ : Box ι
h₁ : J₁ ∈ π
hx₁ : x ∈ Box.Icc J₁
J₂ : Box ι
h₂ : J₂ ∈ π
hx₂ : x ∈ Box.Icc J₂
i : ι
H : ∀ (x_1 : ι), J₁.lower x_1 = x x_1 ↔ J₂.lower x_1 = x x_1
⊢ (Set.Ioc (J₁.lower i) (J₁.upper i) ∩ Set.Ioc (J₂.lower i) (J₂.upper i)).Nonempty
tactic: simp only [Set.ext_iff, mem_setOf] at H
state_before: case intro.intro
ι : Type u_1
I J J₁✝ J₂✝ : Box ι
π π₁ π₂ : Prepartition I
x✝ x : ι → ℝ
J₁ : Box ι
h₁ : J₁ ∈ π
hx₁ : x ∈ Box.Icc J₁
J₂ : Box ι
h₂ : J₂ ∈ π
hx₂ : x ∈ Box.Icc J₂
i : ι
H : ∀ (x_1 : ι), J₁.lower x_1 = x x_1 ↔ J₂.lower x_1 = x x_1
⊢ (Set.Ioc (J₁.lower i) (J₁.upper i) ∩ Set.Ioc (J₂.lower i) (J₂.upper i)).Nonempty
state_after: case intro.intro.inl
ι : Type u_1
I J J₁✝ J₂✝ : Box ι
π π₁ π₂ : Prepartition I
x✝ x : ι → ℝ
J₁ : Box ι
h₁ : J₁ ∈ π
hx₁ : x ∈ Box.Icc J₁
J₂ : Box ι
h₂ : J₂ ∈ π
hx₂ : x ∈ Box.Icc J₂
i : ι
H : ∀ (x_1 : ι), J₁.lower x_1 = x x_1 ↔ J₂.lower x_1 = x x_1
hi₁ : J₁.lower i = x i
⊢ (Set.Ioc (J₁.lower i) (J₁.upper i) ∩ Set.Ioc (J₂.lower i) (J₂.upper i)).Nonempty

case intro.intro.inr
ι : Type u_1
I J J₁✝ J₂✝ : Box ι
π π₁ π₂ : Prepartition I
x✝ x : ι → ℝ
J₁ : Box ι
h₁ : J₁ ∈ π
hx₁ : x ∈ Box.Icc J₁
J₂ : Box ι
h₂ : J₂ ∈ π
hx₂ : x ∈ Box.Icc J₂
i : ι
H : ∀ (x_1 : ι), J₁.lower x_1 = x x_1 ↔ J₂.lower x_1 = x x_1
hi₁ : J₁.lower i < x i
⊢ (Set.Ioc (J₁.lower i) (J₁.upper i) ∩ Set.Ioc (J₂.lower i) (J₂.upper i)).Nonempty
tactic: rcases (hx₁.1 i).eq_or_lt with hi₁ | hi₁