Theorem psseq2i

Description: An equality inference for the proper subclass relationship. (Contributed by NM, 9-Jun-2004)

	Ref	Expression
Hypothesis	psseq1i.1	|- A = B
Assertion	psseq2i	|- ( C C. A <-> C C. B )

Proof

Step	Hyp	Ref	Expression
1		psseq1i.1	|- A = B
2		psseq2	|- ( A = B -> ( C C. A <-> C C. B ) )
3	1 2	ax-mp	|- ( C C. A <-> C C. B )