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
j points away from the origin in the y direction.
从原点指向 y 轴正方向
This is the vertical direction y.
这个是垂直的,Y轨道。
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