And when we're talking about the amplitude of the wave, we're talking about the deviation from that average level. So, if we define the average level as zero, you can have either a positive amplitude or a negative amplitude.

当我们讨论一个波的振幅时,我们说的是偏离平均位置的量,如果我们把平均位置,定义为零的话，那幅值不是,正的就是负的，有时候人们在。

麻省理工公开课 - 化学原理课程节选

It says find the midpoint, which says, last take the start, which is pointing to that place and add it to start. And that basically, somewhere about here, gives me the midpoint.

先找到中点，从起点开始，指向这个位置，用first减去,加上得到偏移量），大概在这里，我们找到了终点。

麻省理工公开课 - 计算机科学及编程导论课程节选