Theorem difeq1i

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

	Ref	Expression
Hypothesis	difeq1i.1	$$⊢A=B$$
Assertion	difeq1i	$$⊢A\setminus C=B\setminus C$$

Proof

Step	Hyp	Ref	Expression
1		difeq1i.1	$$⊢A=B$$
2		difeq1	$$⊢A=B\to A\setminus C=B\setminus C$$
3	1 2	ax-mp	$$⊢A\setminus C=B\setminus C$$