Calculate the area of the big semicircle first. The large semicircle has a diameter of 4cm and a radius of 2cm.

Then the area of the semicircle is1/2uighur r 2 =1/2uighur * 2 2 = 2uighur.

Two small semicircles add up to a circle, so the radius of the two small semicircles is 4/2/2 = 1.

So the sum of the areas of two small semicircles is the area of the circle, which is r 2 = u.

So the shadow area is: 2-5 = 5.