Theorem truimfal 1388

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

Assertion

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

Proof of Theorem truimfal

Step	Hyp	Ref	Expression
1		tru 1335	. . 3 |- T.
2	1	a1bi 242	. 2 |- ( F. <-> ( T. -> F. ) )
3	2	bicomi 131	1 |- ( ( T. -> F. ) <-> F. )

Syntax hints:   -> wi 4   <-> wb 104   T. wtru 1332   F. wfal 1336

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107

This theorem depends on definitions:  df-bi 116  df-tru 1334

This theorem is referenced by:  trubifal  1394