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
⊢ s ⊆ interior s ↔ IsOpen s
simp only [interior_eq_iff_isOpen.symm, Subset.antisymm_iff, interior_subset, true_and]