And then further you put some recording device, which in those days was a photographic plate, far across a room. So you take a tiny, tiny angle and you go far enough across the room.

接着放一些记录设备，那时用的是一个摄影用的感光片，取一个极小极小的角度,然后去到房间中足够远的地方。

麻省理工公开课 - 固态化学导论课程节选

As time increases, the angle increases and we can ask, "How long does it take for the particle to come back to the starting point?"

这个角度随着时间在增加,我们会问,"质点需要多长时间,才能转到起点"

耶鲁公开课 - 基础物理课程节选

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