Theorem nottru

Description: A -. identity. (Contributed by Anthony Hart, 22-Oct-2010)

	Ref	Expression
Assertion	nottru	⊢ ( ¬ ⊤ ↔ ⊥ )

Proof

Step	Hyp	Ref	Expression
1		df-fal	⊢ ( ⊥ ↔ ¬ ⊤ )
2	1	bicomi	⊢ ( ¬ ⊤ ↔ ⊥ )