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Homework Help: Solving difficult integrals

  1. Jul 17, 2011 #1
    1. The problem statement, all variables and given/known data
    I have a problem in part b
    attachment.php?attachmentid=37249&stc=1&d=1310910823.jpg

    2. Relevant equations



    3. The attempt at a solution
    How to integral the function?

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  2. jcsd
  3. Jul 17, 2011 #2
    1. The problem statement, all variables and given/known data
    I would like to ask for 18 and20

    attachment.php?attachmentid=37252&stc=1&d=1310910922.jpg


    2. Relevant equations



    3. The attempt at a solution
    Again how to integral the function?

    attachment.php?attachmentid=37250&stc=1&d=1310910823.jpg

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  4. Jul 17, 2011 #3

    gb7nash

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    Homework Helper

    10a looks fine.

    For 10b, take advantage of the following trig identity:

    cosh2 x = [1 + cosh (2x)]/2
     
  5. Jul 17, 2011 #4
    Oh no, I know this identity, but there are too many identity and formula so I can't remember it before you tell me. How can I make sure that I remember all of them? Or where can I check these useful identity?
     
  6. Jul 17, 2011 #5

    gb7nash

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    Homework Helper

    http://planetmath.org/encyclopedia/HyperbolicIdentities.html [Broken]

    As far as knowing which ones to remember, it would depend on what you're trying to do and what class you're in. For a lot of integral problems, the identities I usually see are sin2 + cos2 = 1 (and any other pythagorean identities), and half/double angle formulas.
     
    Last edited by a moderator: May 5, 2017
  7. Jul 17, 2011 #6
    Thanks so much.
    Shall we move on #2?
    I just have some problems.
     
    Last edited by a moderator: May 5, 2017
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