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Homework Help: Simplifying a cosine + cosine with conjugate denominators

  1. Mar 13, 2013 #1
    1. The problem statement, all variables and given/known data

    -[itex]\frac{1}{2}[/itex][cos([itex]\frac{\pi+\pi n}{\pi+\pi n}[/itex]) + cos([itex]\frac{\pi-\pi n}{\pi-\pi n}[/itex])]

    2. Relevant equations

    cos(u)cos(v) = [itex]\frac{1}{2}[/itex] cos(u+v)+cos(u-v)

    3. The attempt at a solution
    I am attempting to use the above trig function to simplify the first function, but I can't seem to do it properly. Is there another function for when the contents of the cos are equal to its denominator?

    Thanks in advance for all your help!
  2. jcsd
  3. Mar 13, 2013 #2


    Staff: Mentor

    Don't the fractions simplify to 1 for nearly all values of n? BTW, are there any restrictions on n?
  4. Mar 13, 2013 #3
    I keep getting weird numbers. Problem doesn't state any restrictions!
  5. Mar 13, 2013 #4


    Staff: Mentor

    What are you getting?
  6. Mar 13, 2013 #5


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    More to the point, where did that expression come from? I'm guessing almost certainly from an incorrectly worked Fourier Series problem.
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