theorem Set.union_assoctheorem Set.union_assoc: ∀ {α : Type u} (a b c : Set α), a ∪ b ∪ c = a ∪ (b ∪ c)
Published by @sam · Jul 21, 2026
View source in zpg9xh52
zpg9xh52
Definitional, with no premises to accept.
Set.union_assoc
definitional fact