The steps are as follows:

1. Open cad, first draw a 60*60 rectangle, and complete the operation, as follows.

2. Use three-point circle drawing method to draw the figure as shown below, and trim the excess line segments as follows.

3. Mirror the object in the previous step. Note that the mirror center lines of the two mirrors are different. The completion operation is as follows.

4. Use the offset command to offset the bottom line of the rectangle by different distances and trim it, as shown below.

5. Color the graphics and use the LI text window to view the area of ??the colored area and you are done.