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Metamath Proof Explorer

Theorem ssun2

Description: Subclass relationship for union of classes. (Contributed by NM, 30-Aug-1993)

		Ref	Expression
	Assertion	ssun2	$⊢ A \subseteq B \cup A$

Step	Hyp	Ref	Expression
1		ssun1	$⊢ A \subseteq A \cup B$
2		uncom	$⊢ A \cup B = B \cup A$
3	1 2	sseqtri	$⊢ A \subseteq B \cup A$