So we can now take this expression and rewrite it under the condition of du is equal to zero.

我们利用这个公式,并在du=0的条件下将它重写。

麻省理工公开课 - 热力学与动力学课程节选

In fact, I would encourage you to think the way physicists do, even if you don't plan to be a physicist, because that's the easiest way to do this subject, and that is to follow the reasoning behind everything I give you.

其实,即使你们不打算以后当物理学家,我也希望你们能像物理学家一样思考,因为这是学习这门课的捷径,也就是利用我给你的条件一步一步地推导

耶鲁公开课 - 基础物理课程节选