Somehow, when I told you to invert the transformation, some of you had some difficulty.

我上次让你们逆推变换公式的时候,有的同学觉得很困难

耶鲁公开课 - 基础物理课程节选

If you get them backwards, logr you will integrate one over r and will get log r.

如果你逆推的话，对1/r积分得到。

麻省理工公开课 - 固态化学导论课程节选