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Theorem notfal 1570
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 1556 . 2 ¬ ⊥
21bitru 1551 1 (¬ ⊥ ↔ ⊤)
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wb 205  wtru 1543  wfal 1554
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 1545  df-fal 1555
This theorem is referenced by:  trunanfal  1584  falnanfal  1586  truxorfal  1588  falnorfal  1594  wl-1xor  35999  ifpdfnan  41846
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