# Area of ring section closed within a rectangle

I wish to find out the area of a section of a ring which can be acted on my a rectangle 100mm wide by 60mm height. I know the inner diameter,ID and outer diameter,OD of the ring and the width of the ring $\frac{OD-ID}{2}$ will always be below 60mm so the ring will always be within the rectangle.

I thought it would be a simple take one section area away from the other... but it isn't.

http://bayimg.com/EagDkAAeE

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I worked this out in the end by myself.. easier than I thought. Work out the segments areas of both the ID and OD circle. Work out the rectangle area of the remaining central area of the circle. Then minus the larger area from the smaller area. –  Dan Nov 23 '12 at 15:56