来自《耶鲁大学开放课程：基础物理 第1集 第1集》

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  there's trigonometric identities you know from high school.
  你们高中就学过了三角恒等式
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  Pages and pages of them,
  好几页的内容
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  so no one expects you to know all those identities,
  我不要求你们都能记下来
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  but there are a few popular ones we will use.
  但是我们会用到一些著名的恒等式
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  All right. Anything else? Yes?
  好的 还有问题吗 你说
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  Yeah. Midterm will be sometime around 20th of October.
  嗯 期中考试会在十月二十号左右吧
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  I have to find out exactly the right time.
  我还没把具体时间定下来
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  We have 24 lectures for this class
  我们一共上二十四节课
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  and the first 12 roughly will be part of the Midterm,
  期中考试会涉及到前半个学期的课程内容
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  but after the 12th lecture I may wait a week so
  第十二次课之后 我会停一周的课
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  that you have time to do the problems and get the solutions.
  这样你们就有时间来找助教答疑
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  Then I will give you the Midterm. Yes?
  之后再开始其中考试 请说