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Math Help - summation: converge or diverge

  1. #1
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    summation: converge or diverge

    I know that

    cos(n*pi) will diverge, but how about

    [cos(n*pi)] / [sqrt(n)]

    ?

    thanks
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  2. #2
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    Hint: \cos \pi n = (-1)^n.
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  3. #3
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    diverge b/c geometric:

    |-1| = 1 so diverge

    correct logic?
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  4. #4
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    Quote Originally Posted by DINOCALC09 View Post
    diverge b/c geometric:

    |-1| = 1 so diverge

    correct logic?
    It converges by alternating series test.
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