Topic derivations Logical System gentzen 12/22/05 Introduction to Tactics This video is set in the context of the downloadable program, but it applies equally well in the setting of a proof applet. Your browser does not support html5 video. Book traversal links for Help with Simple Tactics ‹ Tutorial 6: What is a derivation and what does it prove? How experts do derivations. Up Tutorial 7: Conditional Proof ›