theorem Set.mem_sInter
theorem Set.mem_sInter: ∀ {α : Type u} {x : α} {S : Set (Set α)}, x ∈ ⋂₀ S ↔ ∀ (t : Set α), t ∈ S → x ∈ t
theorem Set.mem_sInter
theorem Set.mem_sInter: ∀ {α : Type u} {x : α} {S : Set (Set α)}, x ∈ ⋂₀ S ↔ ∀ (t : Set α), t ∈ S → x ∈ t