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I apologise in advance if this is really basic. I have a circle of radius $15$, from which I work out an arc, given an angle of arbitrary value (it's for a computer program). Given that I know the point where the arc starts, how would I go about working out the coordinates of the end point?


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If you know the arc length or the arc measure (the measure of the central angle in the circle that cuts off that arc) and you know the starting point and the center, you can find the ending point by rotating the starting point by the arc measure about the center of the circle. See this answer of mine for more detail on this method.

If you don't know the center, what else do you know about the circle?

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I did know the center, thanks! – mg33 Jul 22 '11 at 23:30
@mg33: Did the formulas in that other answer make sense? – Isaac Jul 22 '11 at 23:33

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