If I place my container of gas on the table here, and I come back an hour later, the pressure needs to be the same when I come back Otherwise it's not equilibrium.

如果我把装气体的容器放在桌子上，一小时以后我再回来时,气体的压强应该是不变的,否则它就不是平衡的。

麻省理工公开课 - 热力学与动力学课程节选

So what I'm doing here is I'm cooling, and then when I'm sitting at a fixed volume and I'm increasing the pressure, what am I doing? I'm heating, right?

对了，因此在这里，需要冷却,而在这里，当体积不变增加压强时？

麻省理工公开课 - 热力学与动力学课程节选

That's another way of saying maintaining velocity if it's not acted upon by a force.

这就是不受外力作用时,速度保持不变的另一种说法

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