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初中《几何》第三册课本及中考题中有一类关于求阴影部分面积的几何题,我们可根据题意,把整个图形中不同形状的图形按一定大小分类,并按对应的图形设未知数,通过列方程组求出结果,这种数形结合将面积转化为方程组的解题方法,我们称之为方程组法.用此法解题新颖别致,思路清晰,简捷明快. 例1 正方形的边长为a,以各边为直径在正方形内画半圆,求所围成的图形(阴影部
There is a class of geometry questions for calculating the area of shadows in textbooks for junior high school’s Geometry Book 3 and examination questions. We can classify the shapes of different shapes in the whole figure by a certain size according to the meaning of the questions, and set the unknown according to the corresponding figure. By solving the equations in the list, this combination of numbers and shapes converts the area into a problem solving method for the system of equations. We call this the equation set method. Using this method, the problem is novel, unique, clear, and simple. Example 1 Square The side length is a, draw a semicircle within the square with each side as a diameter, and find the enclosed figure (shadow part)