1. The distance XZ = XY + YZ = 6, so the radius of the largest semicircle is 3. Hence its area is (1/2)pi32 or A1 = 9pi/2.
The area of the next largest semicircle is A2 = (1/2)pi22 or A2 = 2pi
The area of the smallest semicircle is A3 = (1/2)pi12 or A3 = pi/2
Hence the area of the shaded region = A1 - A2 - A3 = 9pi/2 - 2pi - pi/2 = 2pi