A student-computer dialog for teaching a mathematical proof proved effective when tested in two university physics courses. The objective was to make the beginning or intermediate physics student an active participant in the development of the proof, which concerned the conservation of mechanical energy for a mass moving in one dimension and subject to a force that depends only on position. A suitable computer flow chart was written, then the program was tested in two university settings and feedback was sought from students. The few problems encountered concerned computer terminology and student choice patterns. Thus the student-computer dialog seems useful in teaching mathematical derivations, the staple of many science courses. (RB)