digamma

例句：

1. 1. 二阶导数
   Second derivative
2. 2.二阶导数
   Second order derivative
3. 3. 二阶导数
   Second-order derivative
4. 1. The function's second derivative is zero at point A.
   该函数在点A的二阶导数为零。
5. 2.The second derivative of the function is a constant.
   该函数的二阶导数是一个常数。
6. 3.The second derivative of the function is used to find the critical points.
   该函数的二阶导数用于找到临界点。