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Theorem notfal 1302
Description: A ¬ identity. (Contributed by Anthony Hart, 22-Oct-2010.) (Proof shortened by Andrew Salmon, 13-May-2011.)
Assertion
Ref Expression
notfal (¬ ⊥ ↔ ⊤ )

Proof of Theorem notfal
StepHypRef Expression
1 fal 1249 . 2 ¬ ⊥
21bitru 1254 1 (¬ ⊥ ↔ ⊤ )
Colors of variables: wff set class
Syntax hints:  ¬ wn 3  wb 98  wtru 1243  wfal 1247
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-in1 544  ax-in2 545
This theorem depends on definitions:  df-bi 110  df-tru 1245  df-fal 1248
This theorem is referenced by:  truxorfal  1308  falxortru  1309  falxorfal  1310
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