来自《耶鲁大学开放课程：基础物理 第4集 第4集》

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  Does it screw up everything?
  它能代表所有情况吗
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  It doesn't because the 5 just comes along for the right, everywhere.
  不能 因为 5 只出现在等式的右边
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  And don't think it's 5 x,
  不要认为这是 5 x
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  because this 5 is part of x.
  因为 5 是 x 的一部分
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  So you can multiply your answer by any number you like,
  你的结果可以乘以任意一个数
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  and you pick that number, that reproduces your initial displacement.
  你选定了某个数 它反映了你的初始位移
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  So if you pulled it by 5, you put a 5.
  如果弹簧的拉伸量是 5 你就把 5 代入
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  So, now we're very happy to describe this problem.
  现在我们就能很好地描述这个问题了
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  It is true, you can put sin(t),
  你确实可以增加 sin(t)
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  but I will, in this problem we don't need it.
  但我觉得 在这个问题上我们没必要这么做
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  Here's an answer that does everything you want it to do.
  现在可利用这个结果做所有工作
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  At the initial time, it gives you 5 times cos(0), which is 5;
  在起始时刻 给出 5 cos(0) 即 5