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Theorem nbfal 1449
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 1445 . 2  |-  -. F.
21nbn 349 1  |-  ( -. 
ph 
<->  ( ph  <-> F.  )
)
Colors of variables: wff setvar class
Syntax hints:   -. wn 3    <-> wb 188   F. wfal 1443
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 189  df-tru 1441  df-fal 1444
This theorem is referenced by:  zfnuleu  4549  rusgra0edg  25675  bisym1  31078  aisfina  38204  aifftbifffaibifff  38229  lindslinindsimp2  39562
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