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Theorem fal 1339
Description: The truth value F. is refutable. (Contributed by Anthony Hart, 22-Oct-2010.) (Proof shortened by Mel L. O'Cat, 11-Mar-2012.)
Assertion
Ref Expression
fal  |-  -. F.

Proof of Theorem fal
StepHypRef Expression
1 tru 1336 . . 3  |- T.
21notnoti 635 . 2  |-  -.  -. T.
3 df-fal 1338 . 2  |-  ( F.  <->  -. T.  )
42, 3mtbir 661 1  |-  -. F.
Colors of variables: wff set class
Syntax hints:   -. wn 3   T. wtru 1333   F. wfal 1337
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 1335  df-fal 1338
This theorem is referenced by:  nbfal  1343  bifal  1345  falim  1346  dfnot  1350  notfal  1393  alnex  1476  csbprc  3411  bdnth  13196
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