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Theorem falbitru 1342
Description: A  <-> identity. (Contributed by Anthony Hart, 22-Oct-2010.) (Proof shortened by Andrew Salmon, 13-May-2011.)
Assertion
Ref Expression
falbitru  |-  ( (  F.  <->  T.  )  <->  F.  )

Proof of Theorem falbitru
StepHypRef Expression
1 bicom 191 . 2  |-  ( (  F.  <->  T.  )  <->  (  T.  <->  F.  ) )
2 trubifal 1341 . 2  |-  ( (  T.  <->  F.  )  <->  F.  )
31, 2bitri 240 1  |-  ( (  F.  <->  T.  )  <->  F.  )
Colors of variables: wff set class
Syntax hints:    <-> wb 176    T. wtru 1307    F. wfal 1308
This theorem is referenced by:  falxortru  1350
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8
This theorem depends on definitions:  df-bi 177  df-tru 1310  df-fal 1311
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