Theorem sselii

Description: Membership inference from subclass relationship. (Contributed by NM, 31-May-1999)

	Ref	Expression
Hypotheses	sseli.1	|- A C_ B
	sselii.2	|- C e. A
Assertion	sselii	|- C e. B

Proof

Step	Hyp	Ref	Expression
1		sseli.1	|- A C_ B
2		sselii.2	|- C e. A
3	1	sseli	|- ( C e. A -> C e. B )
4	2 3	ax-mp	|- C e. B