So much of the world, with all that far away, why would separately?
世界那么大,相隔那么远都能在一起,为什么又会分开?
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。
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