Theorem notfal

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

	Ref	Expression
Assertion	notfal	⊢ ( ¬ ⊥ ↔ ⊤ )

Proof

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