Theorem
pm5.42
Theorem *5.42 of [WhiteheadRussell] p. 125. (Contributed by NM, 3-Jan-2005.)
Conclusion
\( \vdash \varphi \rightarrow \psi \rightarrow \chi \leftrightarrow \varphi \rightarrow \psi \rightarrow \varphi \wedge \chi \)
Proof
ibar
imbi2d
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pm5.74i
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