A pair of conics obtained by expanding an equation in Monge's Form in a Maclaurin Series

This gives the equation

Amazingly, the radius of the indicatrix in any direction is equal to the Square Root of the Radius of Curvature in that direction (Coxeter 1969).

**References**

Coxeter, H. S. M. ``Dupin's Indicatrix'' §19.8 in *Introduction to Geometry, 2nd ed.*
New York: Wiley, pp. 363-365, 1969.

© 1996-9

1999-05-24