Editing Hypocycloid (section)

{{Short description|Curve traced by a point on a circle rolling within another circle}}
{{More citations needed|date=November 2011}}

[[File:astroid2.gif|thumb|460px|The red path is a hypocycloid traced as the smaller black circle rolls around inside the larger black circle (parameters are R=4.0, r=1.0, and so k=4, giving an [[astroid]]).]]
In [[geometry]], a '''hypocycloid''' is a special [[plane curve]] generated by the trace of a fixed point on a small [[circle]] that rolls within a larger circle. As the radius of the larger circle is increased, the hypocycloid becomes more like the [[cycloid]] created by rolling a circle on a line.