Theorem pm2.43b

Inference absorbing redundant antecedent. (Contributed by NM, 31-Oct-1995.)

Hypothesis
pm2.43b.1
\( \vdash \psi \rightarrow \varphi \rightarrow \psi \rightarrow \chi \)
Conclusion
\( \vdash \varphi \rightarrow \psi \rightarrow \chi \)
Proof
pm2.43b.1
pm2.43a _
com12 _