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Metamath Proof Explorer

Theorem falbifal

Description: A <-> identity. (Contributed by Anthony Hart, 22-Oct-2010) (Proof shortened by Andrew Salmon, 13-May-2011)

Ref Expression
Assertion falbifal 
|- ( ( F. <-> F. ) <-> T. )

Proof

Step Hyp Ref Expression
1 biid 
 |-  ( F. <-> F. )
2 1 bitru 
 |-  ( ( F. <-> F. ) <-> T. )