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