Theorem falbifal 1467

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 171	. 2 |- ( F. <-> F. )
2	1	bitru 1414	1 |- ( ( F. <-> F. ) <-> T. )

This proof depends on syntax axioms:   <-> wb 105   T. wtru 1403   F. wfal 1407

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108

This proof depends on definitions:  df-bi 117  df-tru 1405

This theorem is used by: (None)