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Theorem notfal 1346
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
StepHypRef Expression
1 fal 1292 . 2  |-  -. F.
21bitru 1297 1  |-  ( -. F.  <-> T.  )
Colors of variables: wff set class
Syntax hints:   -. wn 3    <-> wb 103   T. wtru 1286   F. wfal 1290
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-in1 577  ax-in2 578
This theorem depends on definitions:  df-bi 115  df-tru 1288  df-fal 1291
This theorem is referenced by:  truxorfal  1352  falxortru  1353  falxorfal  1354
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