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Theorem fal 1266
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 1263 . . 3  |- T.
21notnoti 584 . 2  |-  -.  -. T.
3 df-fal 1265 . 2  |-  ( F.  <->  -. T.  )
42, 3mtbir 606 1  |-  -. F.
Colors of variables: wff set class
Syntax hints:   -. wn 3   T. wtru 1260   F. wfal 1264
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 103  ax-ia2 104  ax-ia3 105  ax-in1 554  ax-in2 555
This theorem depends on definitions:  df-bi 114  df-tru 1262  df-fal 1265
This theorem is referenced by:  nbfal  1270  bifal  1272  falim  1273  dfnot  1278  notfal  1321  alnex  1404  csbprc  3290  bdnth  10341
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