Drawing plane curves

odyssey

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Sep 13, 2013
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How can I draw closed plane curves with rotation number (index) equal to 2, 3, -2 and 0?
 
Winding numbers are relative to where the point (observer) is. But it's easy, draw a helical curve around a point counterclockwise until you've rotated around a point the desired number of times, and then close it up. A clockwise turn gives a negative winding number (at least the way I remember learning it). To achieve a winding number of zero, just make sure the point isn't on the inside of the curve.
 
Yes. Well, imagine an annulus around the origin being a "race track" for the curve.. You place your pencil on the annulus (say at the positive x-axis, call it the "finish line") and begin going around the race track counter-clockwise. Every time you reach the finish line again a counter goes up by +1. If you were to at any point go backwards through the finish line, it would mean adding a -1 to the counter.

When you're done driving you close the curve up, attaching it back to where it started. The counter gives the winding number of the curve around the origin.
 
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