Theorem psseq1i

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

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

Proof

Step	Hyp	Ref	Expression
1		psseq1i.1	|- A = B
2		psseq1	|- ( A = B -> ( A C. C <-> B C. C ) )
3	1 2	ax-mp	|- ( A C. C <-> B C. C )