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	⊢ (( ⊥ ↔ ⊥ ) ↔ ⊤ )

Proof of Theorem falbifal

Step	Hyp	Ref	Expression
1		biid 227	. 2 ⊢ ( ⊥ ↔ ⊥ )
2	1	bitru 1326	1 ⊢ (( ⊥ ↔ ⊥ ) ↔ ⊤ )

Syntax hints:   ↔ wb 176   ⊤ wtru 1316   ⊥ wfal 1317

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

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

This theorem is referenced by:  falxorfal  1361