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Homework Help: Calculus II - Determining if Infinite Sequences Converge

  1. Sep 19, 2011 #1

    I'm studying infinite series and was wondering if someone could recommend me a gigantic list of examples of series and proofs of weather they converge or not.
  2. jcsd
  3. Sep 19, 2011 #2
  4. Sep 19, 2011 #3
    It's called your book!

    There are infinitely many series that converge and diverge in your study of infinite series...just saying...
  5. Sep 19, 2011 #4
    I can't find a list on there of series and proofs of why they converge or not.
  6. Sep 19, 2011 #5
    My book only has so many examples and I did all the homework and don't feel like solving more problems and just woundering if someone could recommend a good list that I could look at of many series that I could just go over that is all
  7. Sep 19, 2011 #6
    What you are looking for are probably tests not proofs. Use the link I provided.
  8. Sep 19, 2011 #7
  9. Sep 19, 2011 #8
    ya i saw those but i was like looking for a list of a bunch of series and proofs for why they converge or not because I'm tried of solving problems and think it would be more efficient to just look at a already made list of series and proofs for why they converge or not so that way i can be so familiar with infinite series that I don't have to think twice about which test to use
  10. Sep 19, 2011 #9
    Like I said you are looking for tests not proofs. Proofs would be much more challenging then simply applying theorems. I would say that knowing when to use various tests in much more efficient than trying to memorize a list of series. By the way, when I took Calculus II I developed a fairly simple algorithm to determine which test to use. See if you can come up with one. It is more convenient to know why the test work and when to apply it than to memorize series.
  11. Sep 19, 2011 #10
    The only problem is that
    I don't think there's one algorithm to use that always works?
    And I have a general idea of when to use which test, but am kind of bad at coming up with comparisons for the limit comparison test, your suppose to pick the comparison to be some function that represents the original function as n goes to infinity or like behaves like it?
    and ya I have memorized the tests but was just like looking for a giant list of examples with tests applied to those examples sort of thing so that way I can become more familiar of when to use which test the most effectively
  12. Sep 19, 2011 #11
    For the comparison test you should choose a series that has a very similar form or a series that your are familiar with like the geometric series or the p-series. Also, when you have cos(n) or sin(n) use the fact that they are bounded.
  13. Sep 19, 2011 #12
    For your algorithm try drawing a binary tree. The root node should be the divergence test.
  14. Sep 19, 2011 #13
    so there's an algorithm to apply that always works?
  15. Sep 20, 2011 #14
    Try to come up with your own algorithm that always works for you.
  16. Sep 20, 2011 #15
    Ummm, no. At least not in the sense that if A is an algorithm and you give it a series S as input it will always tell you whether or not it converges. What he means is that you need to actually solve some problems (yes, I know you don't want to; get over it and do it) and see which tests might apply to different series and which tests you should start with. For example, if you are solving an integral, you don't jump straight to trig. substitution or integration by parts, do you? Usually you just try to find an anti-derivative of the integrand, correct?

    Same thing here. However, this requires you to not be lazy and actually SOLVE problems rather than looking at a list.
  17. Sep 20, 2011 #16


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    Homework Helper

    Didn't we discuss this topic last month?


    There is no Philosopher's Stone for this process. You have to work on a variety of series to learn which methods are more likely to work on a new problem, and which are pointless to try. Experience matters in developing the skill.

    As for "gigantic lists of problems" and already worked-out tests, I have not found a source that has both (I know of plenty of books with long lists of series problems and just answers*...). You would need to look for (and study) a number of books and on-line sources that provide worked examples; I've yet to find a "Big Book of Infinite Series (with Convergence Tests!)"...

    *I've even found the one "everyone" steals problems from...
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