Trochoid around a circle

Drag the "α" slider to see the orbiting circle roll around the central circle, or click once on the "α" slider button and use the keyboard up/down to adjust.

The "s" slider determines whether the orbiting circle rolls inside or outside of the central circle.
The "k" slider determines whether the path is drawn by a point on the edge of the orbiting circle (k=1), a point inside the circle (k<1), or a point outside the circle (k>1).
The "R1" and "r2" sliders adjust the radii of the circles.

Jerome A. White, Created with GeoGebra