Theorem re1luk1

luk-1 derived from the Tarski-Bernays-Wajsberg axioms. (Contributed by Anthony Hart, 16-Aug-2011.) (Proof modification is discouraged.) (New usage is discouraged.)

Conclusion

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

Proof

tbw-ax1