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Complex exponential help

  1. May 1, 2004 #1
    This is an easy question but can some else show/tell me how to do it:
    "use the complex exponential series to express cos(2x) in terms of sin(x)"
    I also don't quite understand the 'complex exponential series'. :redface:
  2. jcsd
  3. May 1, 2004 #2
    I mean can someone* show/tell me....
  4. May 2, 2004 #3
    [tex]e^{i\theta} = \cos{\theta} + i\sin{\theta}[/tex]

    [tex]e^{i\theta} + e^{-i\theta} = 2\cos{\theta}[/tex]

    [tex]e^{i\theta} - e^{-i\theta} = 2i\sin{\theta}[/tex]

  5. May 3, 2004 #4
    complex exponential series is just the taylor series for exp except with a complex variable instead of a real one
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