The example to the right is easily done by hand:

Mark every 10 degrees around a circle. Let point C start at 10 degrees and D at 20 degrees, and connect them with a straight line. Increase C by 10 degrees and D by 20 degrees, and connect again. Keep increasing C by 10 and D by 20 degrees, each time drawing a line segment between them.

The shape they trace out is a cardiod.

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