The proper way to draw a vector is to draw an arrow that's got a beginning and it's got an end.

画矢量的正确方法是,画一个有起点和终点的箭头

耶鲁公开课 - 基础物理课程节选

Then, you make an arrow corresponding to B and lay it on the end of this one.

再画一个表示 B 的箭头,把 B 放在 A 的终点

耶鲁公开课 - 基础物理课程节选

Now, you realize that... By the way, when you draw a vector like A, you're supposed to put a little arrow on top.

现在,大家应该发现...,顺便提一下,当你画了一个矢量,比如 A 时,上面要加个小箭头

耶鲁公开课 - 基础物理课程节选

You can draw the arrow corresponding to A.

你可以先画一个表示 A 的箭头

耶鲁公开课 - 基础物理课程节选