Method 1: Cut the four leaves in the middle of the big circle and fill them in some blanks as shown in the figure, and separate them evenly.

Draw a square in the middle and divide the square into two triangles. The area of the triangle is: 8 circle diameter *4 circle radius ÷2= 16 (square centimeter) Square area: 16*2=32 (square centimeter). Subtract the square area (shadow area) from the circular area: 4 * 4 * 3.

Method 2: the excavation and filling method as shown in the figure is still used.

Make a square, and then I won't count. It's hard. I may have miscalculated, but the idea is right. Okay, I'm a little irresponsible. .