left limit

In this paper,it is discussed that piecewise function can also be judged by left-right limit of derived function in division-point s left-right field existing even being equal or not if it is continuous in division-point.

分段函数在分界点处的导数的计算,一般都要求用左、右导数定义及可导的充要条件去判定,本文讨论了分段函数在分界点连续的前提下,也可利用分界点左、右邻域内导函数的左、右极限是否存在且相等来判定,在一定条件下使求导运算更加快捷方便,并从几何上给出了进一步的阐述。