And this is given the value the notation Avogadro's number we call it.

那个值的符号为,我们把它叫做阿伏加德罗氏数。

麻省理工公开课 - 固态化学导论课程节选

I'm using the fact that when you take a cosine and change the angle inside the cosine, it doesn't care. whereas, if you go to the sine and change the angle inside the sine, it becomes minus sine.

我用了一个结论,当你使用余弦函数时,改变角度的正负,函数值不变,而对于正弦函数,改变角度的符号,则函数值也会变号

耶鲁公开课 - 基础物理课程节选