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Printsmc
geometry senior
Problem
The closed curve in the figure is made up of 9 congruent circular arcs each of length , where each of the centers of the corresponding circles is among the vertices of a regular hexagon of side 2. What is the area enclosed by the curve? 
(A)
(B)
(C)
(D)
(E)
Solution
We can draw the hexagon between the centers of the circles, and compute its area. The hexagon is made of equilateral triangles each with length , so the area is: Then, we add the areas of the three sectors outside the hexagon: We now subtract the areas of the three sectors inside the hexagon but outside the figure (which is ) to get the area enclosed in the curved figure: Hence, our answer is and we are done.
Final answer
E