Rolling curve / 12
Hypocycloid
Geometry
A hypocycloid is a hypotrochoid whose pen distance equals the rolling radius (d = r), so the pen sits on the rim of the rolling circle.
x(t) = (R − r)·cos t + r·cos((R − r)/r · t)
y(t) = (R − r)·sin t − r·sin((R − r)/r · t)
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