We keep the same Cartesian coordinate z to indicate the height above the xy plane, however, we use the azimuthal angle, \phi, and the radius, \rho, to describe the position of the proj...We keep the same Cartesian coordinate z to indicate the height above the xy plane, however, we use the azimuthal angle, \phi, and the radius, \rho, to describe the position of the projection of a point onto the xy plane. \phi is the angle between the x axis and the line from the origin to the projection of the point in the xy plane and \rho is the distance between the point and the z axis.
