Because the order of this doesn't matter.

因为字典里元素的顺序无关紧要。

麻省理工公开课 - 计算机科学及编程导论课程节选

In other words, the order of taking the derivatives with respect to pressure and temperature doesn't matter And what this will show is that dS/dp dS/dp at constant temperature, here we saw how entropy varies with volume, this is going to show us how it varies with pressure.

换句话说,对温度和压强的求导顺序无关紧要,结果会表明,恒定温度下的，对应我们上面看到的，熵如何随着体积变化，这个式子告诉我们，熵如何随着压强变化。

麻省理工公开课 - 热力学与动力学课程节选