来自《耶鲁大学开放课程：基础物理 第2集 第2集》

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  if you like, in terms of these two knowns
  你愿意的话 可以用这两个已知量
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  and these coefficients, which are like these numbers,
  和这些系数 比如这些数字
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  3, 2, 4, and 6?
  3 2 4和6
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  You can do that, but we like to get the answer
  你可以那样做 但是我们喜欢
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  the way this gentleman described it,
  用这位同学所说的方法来得到结果
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  because we like to get an answer more readily
  因为我们喜欢更简洁地获得结果
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  than by doing the mundane work.
  而不是通过繁琐的计算
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  The idea that he had was,
  他的方法是这样的
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  if you go from me to you, with a clockwise rotation,
  如果这个矢量从这转到那是顺时针方向
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  you go from you to me by a counterclockwise rotation.
  那么这个矢量转回来就是逆时针方向
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  Therefore, if I go by φ to you,
  因此 如果它转过角度 φ
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  then you must go by -φ to come to me.
  那么必须转过 -φ 角才能回到原处