把所研究的问题根据题目的特点和要求,分成若干类,转化成若干个小问题来解决,这种按不同情况分类,然后再逐一研究解决的数学思想,称之为分类讨论思想.运用于分类讨论的思想解决问题思路清晰,考虑全面,不会漏解、丢解,可以说是中考得分的利器,下面举一例以飧读者.题目(2016年海淀区一模压轴题)在平面直角坐标系xOy中,⊙C的半径为r,P是与圆心C不重合的点,点P关于⊙C的限距点的定义如下:若P’为直线PC与⊙C According to the characteristics and requirements of the subject, the problem under study is divided into several categories and transformed into several small problems to solve. The mathematical thinking classified according to different situations and then studied and studied one by one is called classified discussion thought. Category discussion of thinking to solve the problem clear thinking, consider the full, will not leak, lysis, can be said to score a senior high school entrance examination, the following example to readers. Title (2016 Haidian District, a molded axis) Cartesian Department of xOy, ⊙ C radius r, P is the center of the circle does not coincide with the point P, P on the limit point on the definition of ⊙ C as follows: If P ’for the line PC and ⊙ C