Metamath Proof Explorer

Theorem tbtru

Description: A proposition is equivalent to itself being equivalent to T. . (Contributed by Anthony Hart, 14-Aug-2011)

Ref Expression
Assertion tbtru 
|- ( ph <-> ( ph <-> T. ) )

Proof

Step Hyp Ref Expression
1 tru 
 |-  T.
2 1 tbt 
 |-  ( ph <-> ( ph <-> T. ) )