Theorem trubitru

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

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

Proof

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