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Theorem fal 1296
Description: The truth value is refutable. (Contributed by Anthony Hart, 22-Oct-2010.) (Proof shortened by Mel L. O'Cat, 11-Mar-2012.)
Assertion
Ref Expression
fal ¬ ⊥

Proof of Theorem fal
StepHypRef Expression
1 tru 1293 . . 3
21notnoti 609 . 2 ¬ ¬ ⊤
3 df-fal 1295 . 2 (⊥ ↔ ¬ ⊤)
42, 3mtbir 631 1 ¬ ⊥
Colors of variables: wff set class
Syntax hints:  ¬ wn 3  wtru 1290  wfal 1294
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-in1 579  ax-in2 580
This theorem depends on definitions:  df-bi 115  df-tru 1292  df-fal 1295
This theorem is referenced by:  nbfal  1300  bifal  1302  falim  1303  dfnot  1307  notfal  1350  alnex  1433  csbprc  3325  bdnth  11382
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