Metamath Proof Explorer

Theorem trubitru

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

Ref Expression
Assertion trubitru 
|- ( ( T. <-> T. ) <-> T. )

Proof

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