I want a vector that I want to call the 0 vector.

我就需要这样的一个零矢量

耶鲁公开课 - 基础物理课程节选

You can see from trigonometry and the length of the vector I'm going to call by A.

可以用三角的知识,然后我把矢量的模长记为 A

耶鲁公开课 - 基础物理课程节选

Then, I want to think of a vector that I can call -A.

现在我有一个矢量,我将其称为 -A

耶鲁公开课 - 基础物理课程节选