I am only counting in one direction, 2 so I have to multiply this whole thing by two because I have to count both directions.

因为我只是在一个方向上计数，所以我要把这些所有乘以,因为我们必须考虑到2个方向。

麻省理工公开课 - 固态化学导论课程节选

If two arrows are equal, you cannot be longer in the x direction and correspondingly short in the y direction.

如果要使两个矢量相等,那么即使 x 分量长一些,y 分量相应地小一些也是不行的

耶鲁公开课 - 基础物理课程节选