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Math Help - Finite sum?

  1. #1
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    Smile Finite sum?

    I am doing some problems in sigma notation and two of them have come up with an ERR: INVALID DIM on my calculator screen, the problems were as follows: lower limit = 1, upper limit 1000 and index of summation 1/n, the other one had lower limit = 1 and upper limit = 5000 and index of summation 1/n. Are these sums considered finite? Why?
    Thank you,
    Keith Stevens
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  2. #2
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    Quote Originally Posted by kcsteven View Post
    I am doing some problems in sigma notation and two of them have come up with an ERR: INVALID DIM on my calculator screen, the problems were as follows: lower limit = 1, upper limit 1000 and index of summation 1/n, the other one had lower limit = 1 and upper limit = 5000 and index of summation 1/n. Are these sums considered finite? Why?
    Thank you,
    Keith Stevens
    I think you are misusing some terminology? You are looking for the sum of 1/n as n goes from 1 to 1000 for your first question, yes? Otherwise I can't make sense of it. (The index of summation here is "n", not 1/n. The 1/n would be called the "summand," I believe.)

    Both of these are necessarily finite since we are taking the finite sum of a set of finite numbers. However both of these sums will take a while for your calculator to compute, particularly if you try to do them in "exact" mode.

    I get 7.48547 for the first sum and 9.09451 for the second, which shows just how slowly this series diverges.

    -Dan
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