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Homework Help: Arc length (mostly a problem with integration)

  1. Feb 2, 2009 #1
    1. The problem statement, all variables and given/known data

    Find the arc length oh the graph f(x)=cosx on the integral [0,[tex]\frac{\pi}{2}[/tex]]

    2. Relevant equations

    [tex]\int^{b}_{a}[/tex][tex]\sqrt{1+{f'(x)}^{2}}[/tex]dx

    3. The attempt at a solution

    Alright so I took the derivative of f(x) to get f'(x)=-sinx then I squared it to get sin[tex]^{2}[/tex]x so I could plug it into the formula to get [tex]\int^{\frac{\pi}{2}}_{0}[/tex][tex]\sqrt{1+sin^{2}x}[/tex] the problem is when I try to integrate...well i can't. I tried to use substitution but since i don't have cos[tex]^{2}[/tex]x anywhere I had some issues.
     
  2. jcsd
  3. Feb 2, 2009 #2
    Anybody? Please this is driving me crazy!
     
  4. Feb 2, 2009 #3

    djeitnstine

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    Gold Member

    You can't do it. You have to do a numerical approximation
     
  5. Feb 2, 2009 #4

    djeitnstine

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    Gold Member

    I get 1.910098938245763 with wxmaxima
     
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