no goals
α : Type u
β : Type v
ι : Sort w
a : α
s✝ s₁ s₂ t : Set α
p p₁ p₂ : α → Prop
inst✝ : TopologicalSpace α
s : Set α
⊢ closure s \ frontier s = interior s
rw [frontier, diff_diff_right_self, inter_eq_self_of_subset_right interior_subset_closure]