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Theorem notfal 1664
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 1635 . 2 ¬ ⊥
21bitru 1641 1 (¬ ⊥ ↔ ⊤)
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wb 196  wtru 1629  wfal 1633
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 1631  df-fal 1634
This theorem is referenced by:  trunanfal  1670  falnanfal  1672  truxorfal  1674  ifpdfnan  38329
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