1. The problem statement, all variables and given/known data Charge is uniformly distributed around a ring of radius R = 2.40cm and the resulting electric field magnitude E is measured along the ring's central axis (perpendicular to the plane of the ring). At what distance from the ring's center is E maximum? 2. Relevant equations Therein lies my problem, I'm unsure how to approach this except ink knowing that Calculus can handle it. I know that I need to find the maximum and can obtain it by deriving the equation, finding the value of Z, then plugging it in and deriving a second time. But the only equation I know of here is: E = kqz/(z^2 + R^2)^3/2 3. The attempt at a solution I'm not sure if I have to modify the formula before I derive it or if I only worry about one part of it to derive. If I just derive the formula in terms of z I get a huge mess. What am I missing? I'm not sure where to start.