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Homework Help: Intergration (basic)

  1. May 14, 2009 #1
    1. The problem statement, all variables and given/known data

    hey guys i was wondering if anyone could show my how to intergrate sqrt(x2+9). any help would be greatfully appreciated. the sqaure root is over everything:rolleyes:

    P.s i have looked at table of intergral but cant see one that looks similar.

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. May 14, 2009 #2


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    Use integration by parts with [itex]u=\sqrt{x^2+9}[/itex] and [itex]dv=dx[/itex]...
  4. May 14, 2009 #3
    thanks but i have never used any of those methods before?
  5. May 14, 2009 #4


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    Homework Helper

    You haven't been taught integration by parts yet? Do you know substitutions, if so try [itex]x=3 \sinh u[/itex]. If both these methods are alien to you they probably expect you to compare it to a standard integral somewhere listed in the back or front of your calculus book.
  6. May 14, 2009 #5


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    Yet another way is to let [itex]x= 3tan(\theta)[/itex]. Then [itex]dx= 3sec^2(\theta)[/itex] and [itex]\sqrt{x^2+ 9}= \sqrt{9tan^2(\theta)+ 9}= 3\sqrt{tan^2(\theta)+ 1}= 3sec(\theta)[/itex].
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