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Maclaurin series of tan (e^x -1)

  1. Apr 12, 2014 #1
    1. The problem statement, all variables and given/known data


    for this, my coefficient of x^4 which is 8/4! = 1/3 .. but the ans should be 13/24... can you tell me which part contain mistake?
    https://i.imgur.com/05NnrdM.jpg
    https://i.imgur.com/28Q9o51.jpg


    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Apr 12, 2014 #2

    Dick

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    In your expression for the third derivative you didn't differentiate the dy/dx factor. You've only got part of the product rule there.
     
  4. Apr 12, 2014 #3
    i redo the question, now my coeffiecient of x becomes only 11 but not 13, now which part is wrong?
    https://www.flickr.com/photos/123101228@N03/13809331763/ [Broken]
     
    Last edited by a moderator: May 6, 2017
  5. Apr 12, 2014 #4

    Dick

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    Exactly the same sort of problem. You left out half of a product rule again. Can't YOU find it? You should have four [...] expressions, not three.
     
    Last edited by a moderator: May 6, 2017
  6. Apr 13, 2014 #5
    sorry i really cant find it, i have 2 [ ..... ] for d3y/dx3 , and i have 4 [...] for d4y/dx4 , can you be more specifiec telling me which part is wrong? thanks!!
     
    Last edited: Apr 13, 2014
  7. Apr 13, 2014 #6
    ..

    .........
     
  8. Apr 13, 2014 #7

    Dick

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    That's the problem. Yes, you should have four [...]'s for d4y/dx4. In the image you sent, you don't have four. You have three. You are missing one.
     
  9. Apr 13, 2014 #8
    thanks a lot! i found out i my grave mistake finally!
     
    Last edited: Apr 13, 2014
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