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Homework Help: Phasors, complex numbers, trig. question

  1. Nov 5, 2008 #1
    1. The problem statement, all variables and given/known data
    Two "waves", characterized by cosx and cos^2(x/2) interfere. Using phasors or complex numbers or trigonometry as necessary, aggregate "cosx + 2cos^2(x/2)" - i.e. rewrite as a single cosine.
    2. Relevant equations

    I was told that there is an error in the way this questions was written and that cos is supposed to be cis

    cisθ = cosθ + isinθ

    3. The attempt at a solution

    I don't know what to do. Am I supposed to replace all of the cosines in the original problem with cis?
  2. jcsd
  3. Nov 5, 2008 #2


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    Science Advisor

    If that was what you were told, then yes, that is what you should do. Of course, [itex]cis(\theta)= e^{i\theta}[/itex] and that might be easier to use.
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