Theorem
pm3.14
Theorem *3.14 of [WhiteheadRussell] p. 111. (Contributed by NM, 3-Jan-2005.)
Conclusion
\( \vdash \neg \varphi \vee \neg \psi \rightarrow \neg (\varphi \wedge \psi) \)
Proof
pm3.1
con2i
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