Theorem inss1

Description: The intersection of two classes is a subset of one of them. Part of Exercise 12 of TakeutiZaring p. 18. (Contributed by NM, 27-Apr-1994)

	Ref	Expression
Assertion	inss1	|- ( A i^i B ) C_ A

Proof

Step	Hyp	Ref	Expression
1		elinel1	|- ( x e. ( A i^i B ) -> x e. A )
2	1	ssriv	|- ( A i^i B ) C_ A