where are the Euler angles, is the angle between the vertical -axis and the top's -axis, is the rotation of the top about its own -axis, and the azimuthal of the top's -axis around the vertical -axis. The principal moments of inertia are about the top's own axis, about the top's own axes, and about the top's own -axis. Since the top is symmetric about its -axis, . Here the simple relation for local gravitational potential energy is used where is the acceleration due to gravity, and the centre of mass of the top is a distance from its tip along its -axis.