Theorem: isPreconnected_Icc_aux
File: Mathlib/Topology/Algebra/Order/IntermediateValue.lean

tactic: have xyab : Icc x y ⊆ Icc a b := Icc_subset_Icc hx.1.1 hy.1.2
state_before: α : Type u
β : Type v
γ : Type w
inst✝⁷ : ConditionallyCompleteLinearOrder α
inst✝⁶ : TopologicalSpace α
inst✝⁵ : OrderTopology α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
inst✝¹ : Nonempty γ
inst✝ : DenselyOrdered α
a b x y : α
s t : Set α
hxy : x ≤ y
hs : IsClosed s
ht : IsClosed t
hab : Icc a b ⊆ s ∪ t
hx : x ∈ Icc a b ∩ s
hy : y ∈ Icc a b ∩ t
⊢ Set.Nonempty (Icc a b ∩ (s ∩ t))

tactic: by_contra hst
state_before: α : Type u
β : Type v
γ : Type w
inst✝⁷ : ConditionallyCompleteLinearOrder α
inst✝⁶ : TopologicalSpace α
inst✝⁵ : OrderTopology α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
inst✝¹ : Nonempty γ
inst✝ : DenselyOrdered α
a b x y : α
s t : Set α
hxy : x ≤ y
hs : IsClosed s
ht : IsClosed t
hab : Icc a b ⊆ s ∪ t
hx : x ∈ Icc a b ∩ s
hy : y ∈ Icc a b ∩ t
xyab : Icc x y ⊆ Icc a b
⊢ Set.Nonempty (Icc a b ∩ (s ∩ t))

tactic: suffices : Icc x y ⊆ s
state_before: α : Type u
β : Type v
γ : Type w
inst✝⁷ : ConditionallyCompleteLinearOrder α
inst✝⁶ : TopologicalSpace α
inst✝⁵ : OrderTopology α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
inst✝¹ : Nonempty γ
inst✝ : DenselyOrdered α
a b x y : α
s t : Set α
hxy : x ≤ y
hs : IsClosed s
ht : IsClosed t
hab : Icc a b ⊆ s ∪ t
hx : x ∈ Icc a b ∩ s
hy : y ∈ Icc a b ∩ t
xyab : Icc x y ⊆ Icc a b
hst : ¬Set.Nonempty (Icc a b ∩ (s ∩ t))
⊢ False

tactic: exact hst ⟨y, xyab <| right_mem_Icc.2 hxy, this <| right_mem_Icc.2 hxy, hy.2⟩
state_before: α : Type u
β : Type v
γ : Type w
inst✝⁷ : ConditionallyCompleteLinearOrder α
inst✝⁶ : TopologicalSpace α
inst✝⁵ : OrderTopology α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
inst✝¹ : Nonempty γ
inst✝ : DenselyOrdered α
a b x y : α
s t : Set α
hxy : x ≤ y
hs : IsClosed s
ht : IsClosed t
hab : Icc a b ⊆ s ∪ t
hx : x ∈ Icc a b ∩ s
hy : y ∈ Icc a b ∩ t
xyab : Icc x y ⊆ Icc a b
hst : ¬Set.Nonempty (Icc a b ∩ (s ∩ t))
this : Icc x y ⊆ s
⊢ False

case this
α : Type u
β : Type v
γ : Type w
inst✝⁷ : ConditionallyCompleteLinearOrder α
inst✝⁶ : TopologicalSpace α
inst✝⁵ : OrderTopology α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
inst✝¹ : Nonempty γ
inst✝ : DenselyOrdered α
a b x y : α
s t : Set α
hxy : x ≤ y
hs : IsClosed s
ht : IsClosed t
hab : Icc a b ⊆ s ∪ t
hx : x ∈ Icc a b ∩ s
hy : y ∈ Icc a b ∩ t
xyab : Icc x y ⊆ Icc a b
hst : ¬Set.Nonempty (Icc a b ∩ (s ∩ t))
⊢ Icc x y ⊆ s

tactic: apply (IsClosed.inter hs isClosed_Icc).Icc_subset_of_forall_mem_nhdsWithin hx.2
state_before: case this
α : Type u
β : Type v
γ : Type w
inst✝⁷ : ConditionallyCompleteLinearOrder α
inst✝⁶ : TopologicalSpace α
inst✝⁵ : OrderTopology α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
inst✝¹ : Nonempty γ
inst✝ : DenselyOrdered α
a b x y : α
s t : Set α
hxy : x ≤ y
hs : IsClosed s
ht : IsClosed t
hab : Icc a b ⊆ s ∪ t
hx : x ∈ Icc a b ∩ s
hy : y ∈ Icc a b ∩ t
xyab : Icc x y ⊆ Icc a b
hst : ¬Set.Nonempty (Icc a b ∩ (s ∩ t))
⊢ Icc x y ⊆ s

tactic: rintro z ⟨zs, hz⟩
state_before: case this
α : Type u
β : Type v
γ : Type w
inst✝⁷ : ConditionallyCompleteLinearOrder α
inst✝⁶ : TopologicalSpace α
inst✝⁵ : OrderTopology α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
inst✝¹ : Nonempty γ
inst✝ : DenselyOrdered α
a b x y : α
s t : Set α
hxy : x ≤ y
hs : IsClosed s
ht : IsClosed t
hab : Icc a b ⊆ s ∪ t
hx : x ∈ Icc a b ∩ s
hy : y ∈ Icc a b ∩ t
xyab : Icc x y ⊆ Icc a b
hst : ¬Set.Nonempty (Icc a b ∩ (s ∩ t))
⊢ ∀ (x_1 : α), x_1 ∈ s ∩ Ico x y → s ∈ 𝓝[Ioi x_1] x_1

tactic: have zt : z ∈ tᶜ := fun zt => hst ⟨z, xyab <| Ico_subset_Icc_self hz, zs, zt⟩
state_before: case this.intro
α : Type u
β : Type v
γ : Type w
inst✝⁷ : ConditionallyCompleteLinearOrder α
inst✝⁶ : TopologicalSpace α
inst✝⁵ : OrderTopology α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
inst✝¹ : Nonempty γ
inst✝ : DenselyOrdered α
a b x y : α
s t : Set α
hxy : x ≤ y
hs : IsClosed s
ht : IsClosed t
hab : Icc a b ⊆ s ∪ t
hx : x ∈ Icc a b ∩ s
hy : y ∈ Icc a b ∩ t
xyab : Icc x y ⊆ Icc a b
hst : ¬Set.Nonempty (Icc a b ∩ (s ∩ t))
z : α
zs : z ∈ s
hz : z ∈ Ico x y
⊢ s ∈ 𝓝[Ioi z] z

tactic: have : tᶜ ∩ Ioc z y ∈ 𝓝[>] z := by
  rw [← nhdsWithin_Ioc_eq_nhdsWithin_Ioi hz.2]
  exact mem_nhdsWithin.2 ⟨tᶜ, ht.isOpen_compl, zt, Subset.rfl⟩
state_before: case this.intro
α : Type u
β : Type v
γ : Type w
inst✝⁷ : ConditionallyCompleteLinearOrder α
inst✝⁶ : TopologicalSpace α
inst✝⁵ : OrderTopology α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
inst✝¹ : Nonempty γ
inst✝ : DenselyOrdered α
a b x y : α
s t : Set α
hxy : x ≤ y
hs : IsClosed s
ht : IsClosed t
hab : Icc a b ⊆ s ∪ t
hx : x ∈ Icc a b ∩ s
hy : y ∈ Icc a b ∩ t
xyab : Icc x y ⊆ Icc a b
hst : ¬Set.Nonempty (Icc a b ∩ (s ∩ t))
z : α
zs : z ∈ s
hz : z ∈ Ico x y
zt : z ∈ tᶜ
⊢ s ∈ 𝓝[Ioi z] z

tactic: apply mem_of_superset this
state_before: case this.intro
α : Type u
β : Type v
γ : Type w
inst✝⁷ : ConditionallyCompleteLinearOrder α
inst✝⁶ : TopologicalSpace α
inst✝⁵ : OrderTopology α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
inst✝¹ : Nonempty γ
inst✝ : DenselyOrdered α
a b x y : α
s t : Set α
hxy : x ≤ y
hs : IsClosed s
ht : IsClosed t
hab : Icc a b ⊆ s ∪ t
hx : x ∈ Icc a b ∩ s
hy : y ∈ Icc a b ∩ t
xyab : Icc x y ⊆ Icc a b
hst : ¬Set.Nonempty (Icc a b ∩ (s ∩ t))
z : α
zs : z ∈ s
hz : z ∈ Ico x y
zt : z ∈ tᶜ
this : tᶜ ∩ Ioc z y ∈ 𝓝[Ioi z] z
⊢ s ∈ 𝓝[Ioi z] z

tactic: have : Ioc z y ⊆ s ∪ t := fun w hw => hab (xyab ⟨le_trans hz.1 (le_of_lt hw.1), hw.2⟩)
state_before: case this.intro
α : Type u
β : Type v
γ : Type w
inst✝⁷ : ConditionallyCompleteLinearOrder α
inst✝⁶ : TopologicalSpace α
inst✝⁵ : OrderTopology α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
inst✝¹ : Nonempty γ
inst✝ : DenselyOrdered α
a b x y : α
s t : Set α
hxy : x ≤ y
hs : IsClosed s
ht : IsClosed t
hab : Icc a b ⊆ s ∪ t
hx : x ∈ Icc a b ∩ s
hy : y ∈ Icc a b ∩ t
xyab : Icc x y ⊆ Icc a b
hst : ¬Set.Nonempty (Icc a b ∩ (s ∩ t))
z : α
zs : z ∈ s
hz : z ∈ Ico x y
zt : z ∈ tᶜ
this : tᶜ ∩ Ioc z y ∈ 𝓝[Ioi z] z
⊢ tᶜ ∩ Ioc z y ⊆ s

tactic: exact fun w ⟨wt, wzy⟩ => (this wzy).elim id fun h => (wt h).elim
state_before: case this.intro
α : Type u
β : Type v
γ : Type w
inst✝⁷ : ConditionallyCompleteLinearOrder α
inst✝⁶ : TopologicalSpace α
inst✝⁵ : OrderTopology α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
inst✝¹ : Nonempty γ
inst✝ : DenselyOrdered α
a b x y : α
s t : Set α
hxy : x ≤ y
hs : IsClosed s
ht : IsClosed t
hab : Icc a b ⊆ s ∪ t
hx : x ∈ Icc a b ∩ s
hy : y ∈ Icc a b ∩ t
xyab : Icc x y ⊆ Icc a b
hst : ¬Set.Nonempty (Icc a b ∩ (s ∩ t))
z : α
zs : z ∈ s
hz : z ∈ Ico x y
zt : z ∈ tᶜ
this✝ : tᶜ ∩ Ioc z y ∈ 𝓝[Ioi z] z
this : Ioc z y ⊆ s ∪ t
⊢ tᶜ ∩ Ioc z y ⊆ s

tactic: rw [← nhdsWithin_Ioc_eq_nhdsWithin_Ioi hz.2]
state_before: α : Type u
β : Type v
γ : Type w
inst✝⁷ : ConditionallyCompleteLinearOrder α
inst✝⁶ : TopologicalSpace α
inst✝⁵ : OrderTopology α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
inst✝¹ : Nonempty γ
inst✝ : DenselyOrdered α
a b x y : α
s t : Set α
hxy : x ≤ y
hs : IsClosed s
ht : IsClosed t
hab : Icc a b ⊆ s ∪ t
hx : x ∈ Icc a b ∩ s
hy : y ∈ Icc a b ∩ t
xyab : Icc x y ⊆ Icc a b
hst : ¬Set.Nonempty (Icc a b ∩ (s ∩ t))
z : α
zs : z ∈ s
hz : z ∈ Ico x y
zt : z ∈ tᶜ
⊢ tᶜ ∩ Ioc z y ∈ 𝓝[Ioi z] z

tactic: exact mem_nhdsWithin.2 ⟨tᶜ, ht.isOpen_compl, zt, Subset.rfl⟩
state_before: α : Type u
β : Type v
γ : Type w
inst✝⁷ : ConditionallyCompleteLinearOrder α
inst✝⁶ : TopologicalSpace α
inst✝⁵ : OrderTopology α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
inst✝¹ : Nonempty γ
inst✝ : DenselyOrdered α
a b x y : α
s t : Set α
hxy : x ≤ y
hs : IsClosed s
ht : IsClosed t
hab : Icc a b ⊆ s ∪ t
hx : x ∈ Icc a b ∩ s
hy : y ∈ Icc a b ∩ t
xyab : Icc x y ⊆ Icc a b
hst : ¬Set.Nonempty (Icc a b ∩ (s ∩ t))
z : α
zs : z ∈ s
hz : z ∈ Ico x y
zt : z ∈ tᶜ
⊢ tᶜ ∩ Ioc z y ∈ 𝓝[Ioc z y] z