在初中几何中,三条线段长分别为a,b,c,求证“a=b+c”的证明题是常见问题,尤其对于线段都不在同一直线的情形.本文针对这种情况给出三种基本思路,下面结合一道考试题进行说明.问题如图1,∠B=∠C=90°,AE平分∠DAB,DE平分∠ADC.求证:AD=AB+CD.由于线段AD、AB和CD相互分离,不在同一直线上,因此需要想方设法进行转化,有三种思路.一、将a一分为二此方法将较长线段AD分割成两部分,使 In junior middle school geometry, the proof of “a = b + c ” is a common problem when the length of the three line segments is a, b, c, respectively, especially for the case where the line segments are not all in the same line. Three basic ideas, the following combination of a test questions to explain the problem shown in Figure 1, ∠ B = ∠ C = 90 °, AE bisect ∠ DAB, DE bisect ∠ ADC. And CD separated from each other, not in the same line, so you need to find ways to transform, there are three ideas. First, the a is divided into two This method will be divided into two parts longer AD