有一类关于求阴影部分面积的几何题,我们可以根据题意,把整个图形看成阴影部分、基础图形,如三角形、正方形、菱形等,以及圆或半圆.利用整体代换,求阴影部分的面积。可以起到事半功倍的效果.现举例说明如下: There is a class of geometrical questions about the area of ​​the shaded part. We can think of the whole figure as a shaded part, a basic figure, such as a triangle, a square, a diamond, etc., as well as a circle or a semicircle based on the meaning of the question. Using the whole substitution, the part of the shadow is area. Can play a multiplier effect. Now illustrate as follows: