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Metamath Proof Explorer

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 ⊢ ( ¬ ⊥ ↔ ⊤ )