Theorem falbifal 1349

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 169	. 2 ⊢ (⊥ ↔ ⊥)
2	1	bitru 1296	1 ⊢ ((⊥ ↔ ⊥) ↔ ⊤)

Syntax hints:   ↔ wb 103  ⊤wtru 1285  ⊥wfal 1289

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106

This theorem depends on definitions:  df-bi 115  df-tru 1287

This theorem is referenced by: (None)