Two long parallel cylinders form a capacitor. (Let their cross sections be the images of u=a and u=−a.) If they are held at potentials V0 and −V0, find the potential V(x,y) at points between them. Given that the charge (per unit length) on a cylinder is q=V0/(2a), show that the capacitance (per unit length), that is, q/(2V0), is given by 1/(4arc coshd/2r), where d is the distance between the centers of the two cylinders, and their radii are r.