Theorem falbifal 1353

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

Assertion

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

Proof of Theorem falbifal

Step	Hyp	Ref	Expression
1		biid 227	. 2 |- ( F. <-> F. )
2	1	bitru 1326	1 |- (( F. <-> F. ) <-> T. )

This proof depends on syntax axioms:   <-> wb 176   T. wtru 1316   F. wfal 1317

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This proof depends on definitions:  df-bi 177  df-tru 1319

This theorem is used by:  falxorfal  1361