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Theorem notfal 1561
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 1547 . 2 ¬ ⊥
21bitru 1542 1 (¬ ⊥ ↔ ⊤)
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wb 205  wtru 1534  wfal 1545
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 206  df-tru 1536  df-fal 1546
This theorem is referenced by:  trunanfal  1575  falnanfal  1577  truxorfal  1579  falnorfal  1585  wl-1xor  36864  ifpdfnan  42787
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