Theorem trubitru 1598

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

Assertion

Ref	Expression
trubitru	⊢ ((⊤ ↔ ⊤) ↔ ⊤)

Proof of Theorem trubitru

Step	Hyp	Ref	Expression
1		biid 264	. 2 ⊢ (⊤ ↔ ⊤)
2	1	bitru 1578	1 ⊢ ((⊤ ↔ ⊤) ↔ ⊤)

This proof depends on syntax axioms:   ↔ wb 209  ⊤wtru 1570

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This proof depends on definitions:  df-bi 210  df-tru 1572

This theorem is used by:  truxortru  1614