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Derivative Problem

  1. Nov 1, 2009 #1


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    1. The problem statement, all variables and given/known data

    What's the 39th derivative of cosx?

    2. Relevant equations

    1st dy/dx: -sin x
    2nd: -cosx
    3rd: sinx
    4th; cosx

    3. The attempt at a solution

    So it repeats every 4
    so I used 39/4 and for a remainder of 3 so is is the 3rd one down?

    I got sin x but I don't know if thats the way its supposed to be done ( the remainder is the number of derivative the answer is)
  2. jcsd
  3. Nov 1, 2009 #2
    Yes, this is the way it should be done.
  4. Nov 1, 2009 #3


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    Homework Helper

    sounds reasonable to me
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