Theorem notfal 1404

Description: A -. identity. (Contributed by Anthony Hart, 22-Oct-2010.) (Proof shortened by Andrew Salmon, 13-May-2011.)

Assertion

Ref	Expression
notfal	|- ( -. F. <-> T. )

Proof of Theorem notfal

Step	Hyp	Ref	Expression
1		fal 1350	. 2 |- -. F.
2	1	bitru 1355	1 |- ( -. F. <-> T. )

Syntax hints:   -. wn 3   <-> wb 104   T. wtru 1344   F. wfal 1348

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-in1 604  ax-in2 605

This theorem depends on definitions:  df-bi 116  df-tru 1346  df-fal 1349

This theorem is referenced by:  truxorfal  1410  falxortru  1411  falxorfal  1412