Metamath Proof Explorer

Theorem trubifal

Description: A <-> identity. (Contributed by Anthony Hart, 22-Oct-2010) (Proof shortened by Andrew Salmon, 13-May-2011) (Proof shortened by Wolf Lammen, 10-Jul-2020)

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

Proof

Step Hyp Ref Expression
1 bicom 
 |-  ( ( T. <-> F. ) <-> ( F. <-> T. ) )
2 falbitru 
 |-  ( ( F. <-> T. ) <-> F. )
3 1 2 bitri 
 |-  ( ( T. <-> F. ) <-> F. )