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Theorem truimfal 1317
Description: A identity. (Contributed by Anthony Hart, 22-Oct-2010.) (Proof shortened by Andrew Salmon, 13-May-2011.)
Assertion
Ref Expression
truimfal ((⊤ → ⊥) ↔ ⊥)

Proof of Theorem truimfal
StepHypRef Expression
1 tru 1263 . . 3
21a1bi 236 . 2 (⊥ ↔ (⊤ → ⊥))
32bicomi 127 1 ((⊤ → ⊥) ↔ ⊥)
Colors of variables: wff set class
Syntax hints:  wi 4  wb 102  wtru 1260  wfal 1264
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 103  ax-ia2 104  ax-ia3 105
This theorem depends on definitions:  df-bi 114  df-tru 1262
This theorem is referenced by:  trubifal  1323
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