Theorem pm2.61d2

Inference eliminating an antecedent. (Contributed by NM, 18-Aug-1993.)

Hypotheses
pm2.61d2.1
\( \vdash \varphi \rightarrow \neg \psi \rightarrow \chi \)
pm2.61d2.2
\( \vdash \psi \rightarrow \chi \)
Conclusion
\( \vdash \varphi \rightarrow \chi \)
Proof
pm2.61d2.2
l1
a1i _
\( \vdash \varphi \rightarrow \psi \rightarrow \chi \)
pm2.61d2.1
\( \vdash \varphi \rightarrow \neg \psi \rightarrow \chi \)
pm2.61d l1 _