线与角是几何学习的起点,也是几何中最基础的内容.这部分内容看似比较简单,同学们在解题中,却常因疏忽而出现一些错误的认识.下面我们就来看一看吧.误区一分类讨论方面例1已知A、B、C三点在同一条直线上,线段AB=8,BC=5,M、N分别是AB、BC的中点.求线段MN的长.错解:如图1,MN=MB+BN=1/2 AB+ Line and angle is the starting point of geometric learning, but also the most basic geometric content.This part of the content may seem relatively simple, students in the problem-solving, but often due to negligence and some mistaken understanding.We will take a look at A misunderstanding Category Discussion Example 1 known A, B, C three points in the same line, the line AB = 8, BC = 5, M, N, respectively, is the midpoint of AB, BC Mismatch: As shown in Figure 1, MN = MB + BN = 1/2 AB +