来自《耶鲁大学开放课程：基础物理 第3集 第3集》

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  you can add the arrows by the rule I gave you
  你可以用我教给你们的箭头相接的方法
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  or just add the components of x of the two guys
  或者就将二者的 x 分量相加
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  to get the component of the sum and likewise for the y.
  得到和矢量的 x 分量 y 方向也是这样
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  I mentioned something of increasing importance only later,
  后来我又讲了更重要的知识点
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  which is that you are free to pick another set of axes,
  你可以随意选取另外一个坐标系
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  not in the traditional x and y direction,
  不再是传统的 x 和 y 方向
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  but as an oblique direction.
  而是倾斜过的方向
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  If you do,
  如果这么做
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  the unit vectors are called i prime and j prime,
  单位矢量就是 i' 和 j'
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  the components of the vector change.
  矢量的两个分量也会发生变化
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  You can imagine that if a vector is viewed from an angle,
  你可以想象一下 如果换一个角度观察矢量
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  then its components will vary with the perspective.
  其分量会相应地发生变化