Answers

2014-01-11T20:07:50+08:00
I think that's two semicircles...one with a radius of 2 and one with a radius of 4. Subtracting the area of the one with radius 2 from the one with radius 4 would give you the answer

Area = (area of larger semicircle)-(area of smaller semicircle)
 \frac{1}{2}   \pi (4)^2 - \frac{1}{2}   \pi (2)^2  
6 \pi
1 5 1