If any two chords be drawn through two points on the major axis of an ellipse equidistant from the center. The value of $\mathrm{Tan}\frac{\mathrm{\alpha }}{2}\mathrm{Tan}\frac{\mathrm{\beta }}{2}\mathrm{Tan}\frac{\mathrm{\gamma }}{2}\mathrm{Tan}\frac{\mathrm{\delta }}{2}$ is where $\mathrm{\alpha },\mathrm{\beta },\mathrm{\gamma },\mathrm{\delta }$are the eccentric angles of the extremities of chords.