Theorem nottru

Description: A -. identity. (Contributed by Anthony Hart, 22-Oct-2010)

	Ref	Expression
Assertion	nottru	|- ( -. T. <-> F. )

Proof

Step	Hyp	Ref	Expression
1		df-fal	|- ( F. <-> -. T. )
2	1	bicomi	|- ( -. T. <-> F. )