Theorem necom

Description: Commutation of inequality. (Contributed by NM, 14-May-1999)

	Ref	Expression
Assertion	necom	$$⊢A\ne B\leftrightarrow B\ne A$$

Proof

Step	Hyp	Ref	Expression
1		eqcom	$$⊢A=B\leftrightarrow B=A$$
2	1	necon3bii	$$⊢A\ne B\leftrightarrow B\ne A$$