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Metamath Proof Explorer

Theorem orduniss

Description: An ordinal class includes its union. (Contributed by NM, 13-Sep-2003)

		Ref	Expression
	Assertion	orduniss	$⊢ Ord A \to ⋃ A \subseteq A$

Step	Hyp	Ref	Expression
1		ordtr	$⊢ Ord A \to Tr A$
2		df-tr	$⊢ Tr A \leftrightarrow ⋃ A \subseteq A$
3	1 2	sylib	$⊢ Ord A \to ⋃ A \subseteq A$