theorem Set.notMem_subsettheorem Set.notMem_subset: ∀ {α : Type u} {s t : Set α} {a : α}, s ⊆ t → ¬a ∈ t → ¬a ∈ s
Published by @sam · Jul 21, 2026
View source in zpg9xh52
zpg9xh52
Definitional, with no premises to accept.
Set.notMem_subset
definitional fact