Möbius Strip 
In the plane there is no path which changes orientation
By moving the red dot in the plan, it is not possible to return near the fixed circle, with reversed rotation arrow: the plan is orientable.
By moving the red dot in the plan, it is not possible to return near the fixed circle, with reversed rotation arrow: the plan is orientable.
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Created on: 2001
Last update: 2021-10-20 13:29:02+0100
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