Theorem pm2.41

Theorem *2.41 of [WhiteheadRussell] p. 106. (Contributed by NM, 3-Jan-2005.)

Conclusion
\( \vdash \psi \vee (\varphi \vee \psi) \rightarrow \varphi \vee \psi \)
Proof
l0
olc
id
jaoi l0 _