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	$$⊢C\setminus A=C\setminus B$$

Proof

Step	Hyp	Ref	Expression
1		difeq1i.1	$$⊢A=B$$
2		difeq2	$$⊢A=B\to C\setminus A=C\setminus B$$
3	1 2	ax-mp	$$⊢C\setminus A=C\setminus B$$