Theorem difeq2i

Description: Inference adding difference to the left in a class equality. (Contributed by NM, 15-Nov-2002)

	Ref	Expression
Hypothesis	difeq1i.1	|- A = B
Assertion	difeq2i	|- ( C \ A ) = ( C \ B )

Proof

Step	Hyp	Ref	Expression
1		difeq1i.1	|- A = B
2		difeq2	|- ( A = B -> ( C \ A ) = ( C \ B ) )
3	1 2	ax-mp	|- ( C \ A ) = ( C \ B )