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Bunuel

Four semicircular arcs of length 2π are joined to make the figure above. What is the area of the enclosed region?


A. \(8\pi\)

B. \(8 + 8\pi\)

C. \(16 + 8\pi\)

D. \(16 + 16\pi\)

E. \(24\pi\)



Solution:

We can see that the enclosed region comprises a square in the center and the four semicircles around the square, where the side of the square is the diameter (or twice the radius) of each semicircle. If we can determine the radius of the circle, then we can determine the area of the region.

Since each semicircular arc has a length of 2π, a full circle will have a circumference of 4π, and therefore the radius of the semicircle is 4π/2π = 2. Thus, each semicircle has an area of ½ x π x 2^2 = 2π, and four of them will have a total area of 8π. As mentioned above, the square in the center has a side length equal to the diameter of the semicircles. Thus, the square has a side length of 4 and an area of 4^2 = 16. Therefore, the area of the enclosed region is 16 + 8π.

Answer: C
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