Theorem
pm2.37
Theorem *2.37 of [WhiteheadRussell] p. 105. (Contributed by NM, 6-Mar-2008.)
Conclusion
\( \vdash (\psi \rightarrow \chi) \rightarrow \psi \vee \varphi \rightarrow \varphi \vee \chi \)
Proof
l0
pm2.38
\( \vdash (\psi \rightarrow \chi) \rightarrow \psi \vee \varphi \rightarrow \chi \vee \varphi \)
pm1.4
\( \vdash \chi \vee \varphi \rightarrow \varphi \vee \chi \)
syl6
l0
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