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About the exponential function of series

  1. Oct 4, 2011 #1

    I have a question about the taylor series.I open cosθ function, I forward while making this solution but I can not write as the definition of exponential function. How Can I write this expression as an exponential function. Maybe I can not see something in it..

    Do you have any idea about definition of it ?
  2. jcsd
  3. Oct 5, 2011 #2


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    Homework Helper

    cosθ=(1/2)(exp(i θ)+exp(-i θ))
    where i is an imaginary unit so that i^2=-1.
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