Theorem pm5.41

Theorem *5.41 of [WhiteheadRussell] p. 125. (Contributed by NM, 3-Jan-2005.) (Proof shortened by Wolf Lammen, 12-Oct-2012.)

Conclusion

\( \vdash (\varphi \rightarrow \psi) \rightarrow \varphi \rightarrow \chi \leftrightarrow \varphi \rightarrow \psi \rightarrow \chi \)

Proof

imdi

bicomi _