曲线的凹凸性与曲率。
the unevenness and curvature of the curve.
一、曲线的凹凸性
1、图像凹凸性判断
2、极大值与极小值判断
（此二种判断方法可根据二次函数进行记忆。二次求导后就相当于二次项前系数，根据系数判断图像开口）
(These two judgment methods can be memorized according to quadratic functions.After the second derivation, it is equivalent to the pre-quadratic coefficient, and the image opening is judged according to the coefficient)
二、曲率
1、函数图形的描绘
在判断了图像的凹凸性与极大值极小值后，描绘图像大概走势，并用相应曲线弧表示
After judging the unevenness and maximum minimum of the image, the general trend of the image is depicted and expressed by the corresponding curve arc
2、曲率
（1）曲率公式
（2）特殊曲率
①直线的曲率为0
②圆的曲率等于半径的倒数。半径越小，曲率越大。