Theorem falbifal

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

	Ref	Expression
Assertion	falbifal	⊢ ( ( ⊥ ↔ ⊥ ) ↔ ⊤ )

Proof

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