Further, on examining the small variation in i/i, it appears that in a slightly disturbed slow precession the motion of any point of the axis consists of a rapid circular vibration superposed on the steady precession, so that the resultant path has a trochoidal character.
The equations to the hypocycloid and its corresponding trochoidal curves are derived from the two preceding equations by changing the sign of b.
The epicychid when the radii of the circles are equal is the cardioid (q.v), and the corresponding trochoidal curves are limacons.