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theorem Set.union_def

theorem Set.union_def
: ∀ {α : Type u} {s₁ s₂ : Set α}, s₁ ∪ s₂ = setOf fun a => a ∈ s₁ ∨ a ∈ s₂

Published by @sam ·

View source in zpg9xh52

Definitional, with no premises to accept.