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Trig identity Q

  1. Aug 16, 2007 #1


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    Could someone tell me which trig identity this chap (in a Physics textbook) is using to turn



    sin^2(3Kx/2) - sin^2(Kx/2)

  2. jcsd
  3. Aug 16, 2007 #2


    [tex]=\frac{\cos{(kx)}}{2} - \frac{\cos{(3kx)}}{2} [/tex]

    [tex]=\frac{-1 + \cos{(kx)}}{2} - \frac{-1 + \cos{(3kx)}}{2}[/tex]

    [tex]=\sin^2{(3kx/2) - \sin^2{(kx/2)}[/tex]
  4. Aug 16, 2007 #3


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    Ah... Thank you very much.
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