Let be a circle of radius 8 centered at point , and let be a point on . Let be the set of points such that is contained within , or such that there exists some rectangle containing whose center is on with , and . Find the area of .
Solution
We wish to consider the union of all rectangles with , and , with center on . Consider translating rectangle along the radius to a rectangle now centered at . It is now clear that that every point inside is a translate of a point in , and furthermore, any rectangle translates along the appropriate radius to the same rectangle . We see that the boundary of this region can be constructed by constructing a quarter-circle at each vertex, then connecting these quarter-circles with tangents to form four rectangular regions. Now, splitting our region in to four quarter circles and five rectangles, we compute the desired area to be
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