Metamath Proof Explorer

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 ⊢ ⊥ ↔ ⊥ ↔ ⊤