Theorem negeqi

Description: Equality inference for negatives. (Contributed by NM, 14-Feb-1995)

	Ref	Expression
Hypothesis	negeqi.1	$$⊢A=B$$
Assertion	negeqi	$$⊢-A=-B$$

Proof

Step	Hyp	Ref	Expression
1		negeqi.1	$$⊢A=B$$
2		negeq	$$⊢A=B\to -A=-B$$
3	1 2	ax-mp	$$⊢-A=-B$$