Theorem
pm4.8
Theorem *4.8 of [WhiteheadRussell] p. 122. (Contributed by NM, 3-Jan-2005.)
Conclusion
\( \vdash \varphi \rightarrow \neg \varphi \leftrightarrow \neg \varphi \)
Proof
l0
pm2.01
ax-1
impbii
l0
_
This is the content in the right pane.