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Trig identity

  1. Nov 27, 2006 #1
    Today the professor wrote down the following for use in an integral:

    [tex]\frac{1}{2}cos(2\theta)=sin\theta cos\theta[/tex]

    i am not sure is this is correct. i have tried to prove this and cannot, i have also not found it in an table of trig identities. Is this a valid identity? i am not sure since this prof always makes mistakes
  2. jcsd
  3. Nov 27, 2006 #2
    It should be [tex] \frac{1}{2}\sin 2\theta = \sin\theta \cos\theta [/tex]
  4. Nov 28, 2006 #3


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    He probably meant

    [tex] \int \cos 2\theta = \sin\theta \cos\theta +c [/tex]

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