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Theorem notfal 1425
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 1371 . 2 ¬ ⊥
21bitru 1376 1 (¬ ⊥ ↔ ⊤)
Colors of variables: wff set class
Syntax hints:  ¬ wn 3  wb 105  wtru 1365  wfal 1369
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-in1 615  ax-in2 616
This theorem depends on definitions:  df-bi 117  df-tru 1367  df-fal 1370
This theorem is referenced by:  truxorfal  1431  falxortru  1432  falxorfal  1433
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