Theorem falxorfal

A \/_ identity. (Contributed by David A. Wheeler, 9-May-2015.)

Conclusion
\( \vdash \bot \veebar \bot \leftrightarrow \bot \)
Proof
l0
df-xor
\( \vdash \bot \veebar \bot \leftrightarrow \neg (\bot \leftrightarrow \bot) \)
falbifal
\( \vdash \bot \leftrightarrow \bot \leftrightarrow \top \)
l2
xchbinx l0 _
\( \vdash \bot \veebar \bot \leftrightarrow \neg \top \)
nottru
\( \vdash \neg \top \leftrightarrow \bot \)
bitri l2 _