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Theorem nbfal 1418
Description: The negation of a proposition is equivalent to itself being equivalent to F.. (Contributed by Anthony Hart, 14-Aug-2011.)
Assertion
Ref Expression
nbfal  |-  ( -. 
ph 
<->  ( ph  <-> F.  )
)

Proof of Theorem nbfal
StepHypRef Expression
1 fal 1414 . 2  |-  -. F.
21nbn 347 1  |-  ( -. 
ph 
<->  ( ph  <-> F.  )
)
Colors of variables: wff setvar class
Syntax hints:   -. wn 3    <-> wb 186   F. wfal 1412
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8
This theorem depends on definitions:  df-bi 187  df-tru 1410  df-fal 1413
This theorem is referenced by:  zfnuleu  4524  rusgra0edg  25384  bisym1  30664  aisfina  37474  lindslinindsimp2  38588
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