1. Two semi infinite conducting plates at right angles to each other, we bring in a charge q from infinity to point (a,b) what is the energy involved in doing so? 2. Relevant equations coulomb's law and method of images in griffith. 3. The attempt at a solution force can be easily calculated by method of images which turns out to: F=kq^2 [ 1/(2b)^2 - 1/(2a)^2 + 1/((2b)^2+(2a)^2)^0.5] I can do line integral to this but before that I have to convert them to one single variable, how can i do that ?