5 lines
207 B
Text
5 lines
207 B
Text
def Union {α : Prop} {β : Type} (s : α → set β) (x : β) : Prop :=
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∃ i, x ∈ s i
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example (y : ℕ) (t : set ℕ) : Union (λH : (∃x, x ∈ t), t) y → true
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| ⟨⟨z, z_ex⟩, y_in⟩ := ⟨⟩
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