Theorem 2false

Two falsehoods are equivalent. (Contributed by NM, 4-Apr-2005.) (Proof shortened by Wolf Lammen, 19-May-2013.)

Hypotheses
2false.1
\( \vdash \neg \varphi \)
2false.2
\( \vdash \neg \psi \)
Conclusion
\( \vdash \varphi \leftrightarrow \psi \)
Proof
l0
2false.1
2false.2
2th l0 _
con4bii _