Theorem nne

Description: Negation of inequality. (Contributed by NM, 9-Jun-2006)

	Ref	Expression
Assertion	nne	|- ( -. A =/= B <-> A = B )

Proof

Step	Hyp	Ref	Expression
1		df-ne	|- ( A =/= B <-> -. A = B )
2	1	con2bii	|- ( A = B <-> -. A =/= B )
3	2	bicomi	|- ( -. A =/= B <-> A = B )