Theorem: exists_continuous_one_zero_of_isCompact
File: Mathlib/Topology/UrysohnsLemma.lean

Proof steps:
state_before: X : Type u_1
inst✝² : TopologicalSpace X
inst✝¹ : RegularSpace X
inst✝ : LocallyCompactSpace X
s t : Set X
hs : IsCompact s
ht : IsClosed t
hd : Disjoint s t
⊢ ∃ f, EqOn (⇑f) 1 s ∧ EqOn (⇑f) 0 t ∧ HasCompactSupport ⇑f ∧ ∀ (x : X), f x ∈ Icc 0 1
state_after: case intro.intro.intro.intro
X : Type u_1
inst✝² : TopologicalSpace X
inst✝¹ : RegularSpace X
inst✝ : LocallyCompactSpace X
s t : Set X
hs : IsCompact s
ht : IsClosed t
hd : Disjoint s t
k : Set X
k_comp : IsCompact k
k_closed : IsClosed k
sk : s ⊆ interior k
kt : k ⊆ tᶜ
⊢ ∃ f, EqOn (⇑f) 1 s ∧ EqOn (⇑f) 0 t ∧ HasCompactSupport ⇑f ∧ ∀ (x : X), f x ∈ Icc 0 1
tactic: obtain ⟨k, k_comp, k_closed, sk, kt⟩ : ∃ k, IsCompact k ∧ IsClosed k ∧ s ⊆ interior k ∧ k ⊆ tᶜ :=
    exists_compact_closed_between hs ht.isOpen_compl hd.symm.subset_compl_left
state_before: case intro.intro.intro.intro
X : Type u_1
inst✝² : TopologicalSpace X
inst✝¹ : RegularSpace X
inst✝ : LocallyCompactSpace X
s t : Set X
hs : IsCompact s
ht : IsClosed t
hd : Disjoint s t
k : Set X
k_comp : IsCompact k
k_closed : IsClosed k
sk : s ⊆ interior k
kt : k ⊆ tᶜ
⊢ ∃ f, EqOn (⇑f) 1 s ∧ EqOn (⇑f) 0 t ∧ HasCompactSupport ⇑f ∧ ∀ (x : X), f x ∈ Icc 0 1
state_after: case intro.intro.intro.intro.intro.mk.intro.intro
X : Type u_1
inst✝² : TopologicalSpace X
inst✝¹ : RegularSpace X
inst✝ : LocallyCompactSpace X
s t : Set X
hs : IsCompact s
ht : IsClosed t
hd : Disjoint s t
k : Set X
k_comp : IsCompact k
k_closed : IsClosed k
sk : s ⊆ interior k
kt : k ⊆ tᶜ
f : X → ℝ
hf : Continuous f
hfs : EqOn (⇑{ toFun := f, continuous_toFun := hf }) 0 s
hft : EqOn (⇑{ toFun := f, continuous_toFun := hf }) 1 (interior k)ᶜ
h'f : ∀ (x : X), { toFun := f, continuous_toFun := hf } x ∈ Icc 0 1
⊢ ∃ f, EqOn (⇑f) 1 s ∧ EqOn (⇑f) 0 t ∧ HasCompactSupport ⇑f ∧ ∀ (x : X), f x ∈ Icc 0 1
tactic: rcases exists_continuous_zero_one_of_isCompact hs isOpen_interior.isClosed_compl
    (disjoint_compl_right_iff_subset.mpr sk) with ⟨⟨f, hf⟩, hfs, hft, h'f⟩
state_before: case intro.intro.intro.intro.intro.mk.intro.intro
X : Type u_1
inst✝² : TopologicalSpace X
inst✝¹ : RegularSpace X
inst✝ : LocallyCompactSpace X
s t : Set X
hs : IsCompact s
ht : IsClosed t
hd : Disjoint s t
k : Set X
k_comp : IsCompact k
k_closed : IsClosed k
sk : s ⊆ interior k
kt : k ⊆ tᶜ
f : X → ℝ
hf : Continuous f
hfs : EqOn (⇑{ toFun := f, continuous_toFun := hf }) 0 s
hft : EqOn (⇑{ toFun := f, continuous_toFun := hf }) 1 (interior k)ᶜ
h'f : ∀ (x : X), { toFun := f, continuous_toFun := hf } x ∈ Icc 0 1
⊢ ∃ f, EqOn (⇑f) 1 s ∧ EqOn (⇑f) 0 t ∧ HasCompactSupport ⇑f ∧ ∀ (x : X), f x ∈ Icc 0 1
state_after: case intro.intro.intro.intro.intro.mk.intro.intro
X : Type u_1
inst✝² : TopologicalSpace X
inst✝¹ : RegularSpace X
inst✝ : LocallyCompactSpace X
s t : Set X
hs : IsCompact s
ht : IsClosed t
hd : Disjoint s t
k : Set X
k_comp : IsCompact k
k_closed : IsClosed k
sk : s ⊆ interior k
kt : k ⊆ tᶜ
f : X → ℝ
hf : Continuous f
hfs : EqOn (⇑{ toFun := f, continuous_toFun := hf }) 0 s
hft : EqOn (⇑{ toFun := f, continuous_toFun := hf }) 1 (interior k)ᶜ
h'f : ∀ (x : X), { toFun := f, continuous_toFun := hf } x ∈ Icc 0 1
A : t ⊆ (interior k)ᶜ
⊢ ∃ f, EqOn (⇑f) 1 s ∧ EqOn (⇑f) 0 t ∧ HasCompactSupport ⇑f ∧ ∀ (x : X), f x ∈ Icc 0 1
tactic: have A : t ⊆ (interior k)ᶜ := subset_compl_comm.mpr (interior_subset.trans kt)
state_before: case intro.intro.intro.intro.intro.mk.intro.intro
X : Type u_1
inst✝² : TopologicalSpace X
inst✝¹ : RegularSpace X
inst✝ : LocallyCompactSpace X
s t : Set X
hs : IsCompact s
ht : IsClosed t
hd : Disjoint s t
k : Set X
k_comp : IsCompact k
k_closed : IsClosed k
sk : s ⊆ interior k
kt : k ⊆ tᶜ
f : X → ℝ
hf : Continuous f
hfs : EqOn (⇑{ toFun := f, continuous_toFun := hf }) 0 s
hft : EqOn (⇑{ toFun := f, continuous_toFun := hf }) 1 (interior k)ᶜ
h'f : ∀ (x : X), { toFun := f, continuous_toFun := hf } x ∈ Icc 0 1
A : t ⊆ (interior k)ᶜ
⊢ ∃ f, EqOn (⇑f) 1 s ∧ EqOn (⇑f) 0 t ∧ HasCompactSupport ⇑f ∧ ∀ (x : X), f x ∈ Icc 0 1
state_after: case intro.intro.intro.intro.intro.mk.intro.intro.refine_1
X : Type u_1
inst✝² : TopologicalSpace X
inst✝¹ : RegularSpace X
inst✝ : LocallyCompactSpace X
s t : Set X
hs : IsCompact s
ht : IsClosed t
hd : Disjoint s t
k : Set X
k_comp : IsCompact k
k_closed : IsClosed k
sk : s ⊆ interior k
kt : k ⊆ tᶜ
f : X → ℝ
hf : Continuous f
hfs : EqOn (⇑{ toFun := f, continuous_toFun := hf }) 0 s
hft : EqOn (⇑{ toFun := f, continuous_toFun := hf }) 1 (interior k)ᶜ
h'f : ∀ (x : X), { toFun := f, continuous_toFun := hf } x ∈ Icc 0 1
A : t ⊆ (interior k)ᶜ
⊢ HasCompactSupport ⇑{ toFun := fun x => 1 - f x, continuous_toFun := ⋯ }

case intro.intro.intro.intro.intro.mk.intro.intro.refine_2
X : Type u_1
inst✝² : TopologicalSpace X
inst✝¹ : RegularSpace X
inst✝ : LocallyCompactSpace X
s t : Set X
hs : IsCompact s
ht : IsClosed t
hd : Disjoint s t
k : Set X
k_comp : IsCompact k
k_closed : IsClosed k
sk : s ⊆ interior k
kt : k ⊆ tᶜ
f : X → ℝ
hf : Continuous f
hfs : EqOn (⇑{ toFun := f, continuous_toFun := hf }) 0 s
hft : EqOn (⇑{ toFun := f, continuous_toFun := hf }) 1 (interior k)ᶜ
h'f : ∀ (x : X), { toFun := f, continuous_toFun := hf } x ∈ Icc 0 1
A : t ⊆ (interior k)ᶜ
x : X
⊢ { toFun := fun x => 1 - f x, continuous_toFun := ⋯ } x ∈ Icc 0 1
tactic: refine ⟨⟨fun x ↦ 1 - f x, continuous_const.sub hf⟩, fun x hx ↦ by simpa using hfs hx,
    fun x hx ↦ by simpa [sub_eq_zero] using (hft (A hx)).symm, ?_, fun x ↦ ?_⟩