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Arc length integral

  1. Mar 27, 2009 #1
    1. The problem statement, all variables and given/known data

    ok, the original prob is : find the length of the curve of y=ln(1-x^2) x between 0, 1/2.



    2. Relevant equations



    3. The attempt at a solution
    ive made it this far: my integral is -1 + 2/1-x^2..............ok so i decompose the second part but in doing so i get a negative to make it -(x+1)(x-1) but i don't know what happens to that negative because the solution manual says the integral is .......-1+ 1/x+1 -1/x-1 dx i don't get the signs. please help!
     
  2. jcsd
  3. Mar 27, 2009 #2
    if we are woking with single variable functions, y=f(x) like here then the arc length from a to be of a curve is:


    [tex]L=\int_a^b\sqrt{1+[f'(x)]^2}dx[/tex]
     
  4. Mar 27, 2009 #3
    yes....like i said ive already worked that part....im toward the end of the problem i just don't get the signs
     
  5. Mar 27, 2009 #4
    Well, since you have shown almost no work(step by step) it is hard to tell where you have missed, or what you are doing wrong.
     
  6. Mar 27, 2009 #5
    got it...nvm..thanks
     
  7. Mar 27, 2009 #6
    :cool:
     
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