And, as before, this comes from the fact that the mixed second derivatives are the same, no matter in which order you take them.

和以前一样，它来源于这样一个事实，混合二阶导数，求导次序改变，结果不变。

youdao

And, as before, this comes from the fact that the mixed second derivatives are the same, no matter in which order you take them.

和以前一样，它来源于这样一个事实，混合二阶导数，求导次序改变，结果不变。

youdao