Theorem
pm2.3
Theorem *2.3 of [WhiteheadRussell] p. 104. (Contributed by NM, 3-Jan-2005.)
Conclusion
\( \vdash \varphi \vee (\psi \vee \chi) \rightarrow \varphi \vee (\chi \vee \psi) \)
Proof
pm1.4
orim2i
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