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HELP! how to plug this into the calculator sigma notation?

  1. Aug 10, 2010 #1
    how would i plug this into the calculator? to find the sum?
    step by step process? thankss!

    ∑ 2 cos (π/k)
    k = 1

    i tried this site
    http://mathbits.com/mathbits/tisection/Algebra2/summation.htm [Broken]
    and i got a different answer...so i just need help with the set up on a T.I calc.
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Aug 10, 2010 #2


    Staff: Mentor

    Why would you want to? This is a summation with four terms. Just expand the summation into its four terms.
  4. Aug 11, 2010 #3


    User Avatar
    Science Advisor

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

    Since [itex]cos(\pi)= -1[/itex], [itex]cos(\pi/2)= 0[/itex], [itex]cos(\pi/3)= 1/2[/itex], and [itex]cos(\pi/4)= \sqrt{2}/2[/itex], you shouldn't need to use a calculator.
  5. Aug 12, 2010 #4
    for the function f(x) for x=a to x=b the screen should read


    you should be able to catalog or 2nd[math] to find the [sum(] and [seq(] operators

    hope this helps
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