Theorem exp4b

An exportation inference. (Contributed by NM, 26-Apr-1994.) (Proof shortened by Wolf Lammen, 23-Nov-2012.) Shorten exp4a. (Revised by Wolf Lammen, 20-Jul-2021.)

Hypothesis
exp4b.1
\( \vdash \varphi \wedge \psi \rightarrow \chi \wedge \theta \rightarrow \tau \)
Conclusion
\( \vdash \varphi \rightarrow \psi \rightarrow \chi \rightarrow \theta \rightarrow \tau \)
Proof
exp4b.1
expd _
ex _