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.
