2003 AMC 12B Problem 16
Problem 16 of 25IntermediateGeometry
Three semicircles of radius are constructed on diameter of a semicircle of radius The centers of the small semicircles divide into four line segments of equal length, as shown. What is the area of the shaded region that lies within the large semicircle but outside the smaller semicircles?

Answer choices
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Solution
The large semicircle has area
The three small semicircles have total area before their overlaps are accounted for. The centers of each adjacent pair are unit apart, so their intersection is bounded by two sectors and an equilateral triangle. Each of the two overlaps therefore has area
The shaded area is
Thus, the correct answer is E.