Theorem pm5.53

Theorem *5.53 of [WhiteheadRussell] p. 125. (Contributed by NM, 3-Jan-2005.)

Conclusion
\( \vdash \varphi \vee \psi \vee \chi \rightarrow \theta \leftrightarrow (\varphi \rightarrow \theta) \wedge (\psi \rightarrow \theta) \wedge (\chi \rightarrow \theta) \)
Proof
l0
jaob
\( \vdash \varphi \vee \psi \vee \chi \rightarrow \theta \leftrightarrow (\varphi \vee \psi \rightarrow \theta) \wedge (\chi \rightarrow \theta) \)
jaob
\( \vdash \varphi \vee \psi \rightarrow \theta \leftrightarrow (\varphi \rightarrow \theta) \wedge (\psi \rightarrow \theta) \)
bianbi l0 _