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Calculators Sum of series in Ti-89

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  1. Apr 23, 2012 #1
    Hey, I'm having trouble with plugging sum series into my Ti-89, and was wondering how to do it with things converging and going to infinity. I have the sums rounded to 3 decimal places that my professor gave me, however, I can't figure out how to get it from the calculator. For example I have,

    Ʃ10(n^2)/(n^4+12)=5.960

    On the worksheet it says assume each summation goes from 1 to infinity. It doesn't give me my step size, so I'm assuming it's one?

    I know the command is:
    sum(seq(function, variable, start, stop, step size))

    and so I have:

    sum(seq((10y^2)/(y^4+12),y,1,∞,1))

    and it's telling me that I have a domain error.

    So I tried different stops such as stuff lower than 100 and it works. So my question is how do I get the sum from 1 to infinity? Do I have to improvise and use finite stops (for example 50, etc.)? And then interpret the answer to find the real sum?

    Thanks!
     
  2. jcsd
  3. Apr 23, 2012 #2
    or if I do:
    sum((10y^2)/(y^4+12),y,1,∞,1)

    it returns

    10Ʃ(10y^2)/(y^4+12)
    y=1

    without giving me the answer (even if I hit diamond).
     
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