And that is why I said that we will have an easy formula for n dS while n and dS taken separately are more complicated.because you would have to actually take the length of a direction of this guy.

这就是为什么ndS一起算时,会有一个简单的公式,而当分别计算n和dS时候，会更复杂的,因为必须取这玩意在某个方向上的长度。

youdao

And that is why I said that we will have an easy formula for n dS while n and dS taken separately are more complicated.because you would have to actually take the length of a direction of this guy.

这就是为什么ndS一起算时,会有一个简单的公式,而当分别计算n和dS时候，会更复杂的,因为必须取这玩意在某个方向上的长度。

youdao