分类思想是数学中重要的思想方法。在小学数学教学中，蕴含了这一思想方法，为了适应培养跨世纪人才的需要，初中平几教学中，分类思想方法又有进一步渗透和应用。例如，初中《几何》第一册第１３节“线段的比较和画法”中，为了比较线段ＡＢ和线段ＣＤ的长短，我们可以... The idea of ​​classification is an important way of thinking in mathematics. In primary school mathematics teaching, this thought method is contained. In order to adapt to the needs of cultivating trans-century talents, in the teaching of junior middle school, several methods of classification and thought have been further penetrated and applied. For example, in the “comparison and drawing method of line segments” in Section 1 of Section 3 of Geometry of Junior High School, we can compare the lengths of line segment AB and line segment CD.