Re: [touch-events] rotationAngle range of 0-90 seems counterintuitive - add a diagram? (#53)

If the angle interval was [0,180) instead of [0,90), every ellipse
  (radiusX, radiusY, rotationAngle) = (a, b, theta),
where a!=b and 0<=theta<90, would have another valid representation:
  (b, a, theta+90).
Then any use-case that needs unique representations would have to compute a canonical one.

We shouldn't add a diagram for the what-if-180-degree case for sure. I think we can simply add the following text in the description of rotationAngle:
"The angle interval [0,90) guarantees that any non-circular ellipse is represented by a unique tuple (radiusX, radiusY, rotationAngle)."


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