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Homework Help: Write the sum without sigma notation and evaluate it?

  1. Aug 9, 2010 #1
    ∑ 2cos (π/k)
    k = 1

    i have the answer..but all i need it the steps on how to figure it out!
  2. jcsd
  3. Aug 9, 2010 #2
    It's a finite sum...

    [tex]\sum_{k=1}^4 2 \cos(\pi/k) = 2 \cos(\pi/1) + 2 \cos(\pi/2) + 2 \cos(\pi/3) + 2 \cos(\pi/4)[/tex]

  4. Aug 9, 2010 #3


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    Science Advisor

    It is not a question of "figuring it out", it is just a question of knowing what that notation means.

    It means exactly what adriank said: replace the "k" in [itex]cos(\pi/k)[itex] with 1, 2, 3, and 4 and then add.
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