Theorem: interior_frontier
File: Mathlib/Topology/Basic.lean

tactic: have A : frontier s = s \ interior s := h.frontier_eq
state_before: X : Type u
Y : Type v
ι : Sort w
α : Type u_1
β : Type u_2
x : X
s s₁ s₂ t : Set X
p p₁ p₂ : X → Prop
inst✝ : TopologicalSpace X
h : IsClosed s
⊢ interior (frontier s) = ∅
state_after: X : Type u
Y : Type v
ι : Sort w
α : Type u_1
β : Type u_2
x : X
s s₁ s₂ t : Set X
p p₁ p₂ : X → Prop
inst✝ : TopologicalSpace X
h : IsClosed s
A : frontier s = s \ interior s
⊢ interior (frontier s) = ∅

tactic: have B : interior (frontier s) ⊆ interior s := by rw [A]; exact interior_mono diff_subset
state_before: X : Type u
Y : Type v
ι : Sort w
α : Type u_1
β : Type u_2
x : X
s s₁ s₂ t : Set X
p p₁ p₂ : X → Prop
inst✝ : TopologicalSpace X
h : IsClosed s
A : frontier s = s \ interior s
⊢ interior (frontier s) = ∅
state_after: X : Type u
Y : Type v
ι : Sort w
α : Type u_1
β : Type u_2
x : X
s s₁ s₂ t : Set X
p p₁ p₂ : X → Prop
inst✝ : TopologicalSpace X
h : IsClosed s
A : frontier s = s \ interior s
B : interior (frontier s) ⊆ interior s
⊢ interior (frontier s) = ∅

tactic: have C : interior (frontier s) ⊆ frontier s := interior_subset
state_before: X : Type u
Y : Type v
ι : Sort w
α : Type u_1
β : Type u_2
x : X
s s₁ s₂ t : Set X
p p₁ p₂ : X → Prop
inst✝ : TopologicalSpace X
h : IsClosed s
A : frontier s = s \ interior s
B : interior (frontier s) ⊆ interior s
⊢ interior (frontier s) = ∅
state_after: X : Type u
Y : Type v
ι : Sort w
α : Type u_1
β : Type u_2
x : X
s s₁ s₂ t : Set X
p p₁ p₂ : X → Prop
inst✝ : TopologicalSpace X
h : IsClosed s
A : frontier s = s \ interior s
B : interior (frontier s) ⊆ interior s
C : interior (frontier s) ⊆ frontier s
⊢ interior (frontier s) = ∅

tactic: have : interior (frontier s) ⊆ interior s ∩ (s \ interior s) :=
  subset_inter B (by simpa [A] using C)
state_before: X : Type u
Y : Type v
ι : Sort w
α : Type u_1
β : Type u_2
x : X
s s₁ s₂ t : Set X
p p₁ p₂ : X → Prop
inst✝ : TopologicalSpace X
h : IsClosed s
A : frontier s = s \ interior s
B : interior (frontier s) ⊆ interior s
C : interior (frontier s) ⊆ frontier s
⊢ interior (frontier s) = ∅
state_after: X : Type u
Y : Type v
ι : Sort w
α : Type u_1
β : Type u_2
x : X
s s₁ s₂ t : Set X
p p₁ p₂ : X → Prop
inst✝ : TopologicalSpace X
h : IsClosed s
A : frontier s = s \ interior s
B : interior (frontier s) ⊆ interior s
C : interior (frontier s) ⊆ frontier s
this : interior (frontier s) ⊆ interior s ∩ (s \ interior s)
⊢ interior (frontier s) = ∅

tactic: rwa [inter_diff_self, subset_empty_iff] at this
state_before: X : Type u
Y : Type v
ι : Sort w
α : Type u_1
β : Type u_2
x : X
s s₁ s₂ t : Set X
p p₁ p₂ : X → Prop
inst✝ : TopologicalSpace X
h : IsClosed s
A : frontier s = s \ interior s
B : interior (frontier s) ⊆ interior s
C : interior (frontier s) ⊆ frontier s
this : interior (frontier s) ⊆ interior s ∩ (s \ interior s)
⊢ interior (frontier s) = ∅
state_after: no goals

tactic: rw [A]
state_before: X : Type u
Y : Type v
ι : Sort w
α : Type u_1
β : Type u_2
x : X
s s₁ s₂ t : Set X
p p₁ p₂ : X → Prop
inst✝ : TopologicalSpace X
h : IsClosed s
A : frontier s = s \ interior s
⊢ interior (frontier s) ⊆ interior s
state_after: X : Type u
Y : Type v
ι : Sort w
α : Type u_1
β : Type u_2
x : X
s s₁ s₂ t : Set X
p p₁ p₂ : X → Prop
inst✝ : TopologicalSpace X
h : IsClosed s
A : frontier s = s \ interior s
⊢ interior (s \ interior s) ⊆ interior s

tactic: exact interior_mono diff_subset
state_before: X : Type u
Y : Type v
ι : Sort w
α : Type u_1
β : Type u_2
x : X
s s₁ s₂ t : Set X
p p₁ p₂ : X → Prop
inst✝ : TopologicalSpace X
h : IsClosed s
A : frontier s = s \ interior s
⊢ interior (s \ interior s) ⊆ interior s
state_after: no goals

tactic: simpa [A] using C
state_before: X : Type u
Y : Type v
ι : Sort w
α : Type u_1
β : Type u_2
x : X
s s₁ s₂ t : Set X
p p₁ p₂ : X → Prop
inst✝ : TopologicalSpace X
h : IsClosed s
A : frontier s = s \ interior s
B : interior (frontier s) ⊆ interior s
C : interior (frontier s) ⊆ frontier s
⊢ interior (frontier s) ⊆ s \ interior s
state_after: no goals