Hypotrochoid
Appearance
A hypotrochoid is a roulette traced by a point attached to a circle of radius r rolling around the inside of a fixed circle of radius R, where the point is a distance d from the center of the interior circle.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/f/fa/HypotrochoidOutThreeFifths.gif/250px-HypotrochoidOutThreeFifths.gif)
The parametric equations for a hypotrochoid are:
Special cases include the hypocycloid with d = r and the ellipse with R = 2r.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/5/5c/Ellipse_as_hypotrochoid.gif/220px-Ellipse_as_hypotrochoid.gif)
The classic Spirograph toy traces out hypotrochoid and epitrochoid curves.
See also
References
- J. Dennis Lawrence (1972). A catalog of special plane curves. Dover Publications. pp. 165–168. ISBN 0-486-60288-5.
External links
- Flash Animation of Hypocycloid
- Hypotrochoid from Visual Dictionary of Special Plane Curves, Xah Lee.