In studying form my EM midterm, I came across a practice problem involving finding the potential along the z axis due to a charged disc centered on the same axis. After thinking about the problem a bit, I turned to what's becoming one of my favorite online references, Dr. J.B. Tatum's text on electricity and magnetism [2]. Sure enough, there was a solution that could be adapted to the task at hand. It involved several 'clever' trig substitutions one of which were not immediately clear to me, so I've expanded upon it here. After the clever trig trick, read on to find out more interesting stuff about Dr. Tatum, an emeritus professor at the University of Victoria [1]. The Basic Problem The practice problem mentioned above is described by the following diagram from Dr. Tatum's text. The first and handiest innovation in Dr. Tatum's treatment is to parameterize the problem using the angle marked as theta and the limit of that angle labeled as alpha. T...