Theorem jao

Disjunction of antecedents. Compare Theorem *3.44 of [WhiteheadRussell] p. 113. (Contributed by NM, 5-Apr-1994.) (Proof shortened by Wolf Lammen, 4-Apr-2013.)

Conclusion

\( \vdash (\varphi \rightarrow \psi) \rightarrow (\chi \rightarrow \psi) \rightarrow \varphi \vee \chi \rightarrow \psi \)

Proof

pm3.44

ex _