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Theorem notfal 1559
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 1530 . 2 ¬ ⊥
21bitru 1536 1 (¬ ⊥ ↔ ⊤)
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wb 196  wtru 1524  wfal 1528
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 197  df-tru 1526  df-fal 1529
This theorem is referenced by:  trunanfal  1565  falnanfal  1567  truxorfal  1569  ifpdfnan  38148
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