Two concentric circles are given.
geometry/annulus.chord New
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Problem
Two concentric circles are given. A tangent to the inner circle forms a chord twelve inches long in the larger circle. Find the area of the ring between the circles. -- Joseph <cschen@xnet.com>
Show solution
Since the implication is that the values of the radii of the circles don't matter, I can pick the size of the smaller circle to be anything I want. By picking the inner circle to be infinitesimally small, the 12 inch "chord" becomes the diameter of the larger circle, so it will have a 6 inch radius. A circle with a 6 inch radius has an area of 36*pi square inches. Therefore, the area of the ring between the circles is 36*pi square inches. -- Richard Walter <rwalter@auspex.com>