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Theorem falimfal 1680
Description: A identity. (Contributed by Anthony Hart, 22-Oct-2010.) An alternate proof is possible using falim 1671 instead of id 22 but the present proof using id 22 emphasizes that the result does not require the principle of explosion. (Proof modification is discouraged.)
Assertion
Ref Expression
falimfal ((⊥ → ⊥) ↔ ⊤)

Proof of Theorem falimfal
StepHypRef Expression
1 id 22 . 2 (⊥ → ⊥)
21bitru 1663 1 ((⊥ → ⊥) ↔ ⊤)
Colors of variables: wff setvar class
Syntax hints:  wi 4  wb 198  wtru 1654  wfal 1666
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 199  df-tru 1657
This theorem is referenced by: (None)
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