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Metamath Proof Explorer

Theorem snssi

Description: The singleton of an element of a class is a subset of the class. (Contributed by NM, 6-Jun-1994)

		Ref	Expression
	Assertion	snssi	$⊢ A \in B \to \{A\} \subseteq B$

Step	Hyp	Ref	Expression
1		snssg	$⊢ A \in B \to (A \in B \leftrightarrow \{A\} \subseteq B)$
2	1	ibi	$⊢ A \in B \to \{A\} \subseteq B$