The position of a point P can be specified using Cartesian coordinates (x, y, z) or spherical coordinates (r, y, X), where r is the radial distance of P from origin of the {,, 2} coordinate system. Angles and y denote azimuth and elevation angles respectively as shown in the below figure. The unit vectors {i, j, k} form the spherical coordinate system to represent any arbitrary point P on the sphere. (31 (2, 4,2) K d } d}