Theorem falbifal 1413

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 170	. 2 ⊢ (⊥ ↔ ⊥)
2	1	bitru 1360	1 ⊢ ((⊥ ↔ ⊥) ↔ ⊤)

Syntax hints:   ↔ wb 104  ⊤wtru 1349  ⊥wfal 1353

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 1351

This theorem is referenced by: (None)