Problem 4 (10%) Refer to the following figure and prove the law of Cosines,.

b.(10%) Write the electric intensities () for a point on the ZX-plane in terms of d and R, or d and r, as indicated in (b). P(x, y, z) (x0, d. 0) Grounded plane conductor (ImageCharge) (a) Physical arrangement. (b) Image charge and field lines. Figures (a) and (b) a single charge Q above a ground plane Problem 2 A air-filled coaxial with dimensions as shown in the following figure: