A pair of conics obtained by expanding an equation in Monge's form 
in a Maclaurin series
This gives the equation
 |
(3)
|
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).
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References
Coxeter, H. S. M. "Dupin's Indicatrix" §19.8 in Introduction
to Geometry, 2nd ed. New York: Wiley, pp. 363-365, 1969.Referenced
on Wolfram|Alpha
Dupin's Indicatrix
Cite this as:
Weisstein, Eric W. "Dupin's Indicatrix."
From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/DupinsIndicatrix.html
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