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Homework Help: Line integral of sin cos function

  1. Jun 30, 2011 #1
    1. The problem statement, all variables and given/known data

    integral (sin^4(x) + cos^4(x))^.5 dx

    2. Relevant equations

    sin^2(x) = (1 - cos^2(x))

    3. The attempt at a solution

    cos^4(x) + {1 - cos^2(x)}^2 = 2cos^4(x) -2cos^2(x) + 1
    subst u = cos^2(x)
    integral (2u^2 - 2u +1)^.5
  2. jcsd
  3. Jun 30, 2011 #2


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    hi jbowers9! :smile:

    (have a square-root: √ and try using the X2 icon just above the Reply box :wink:)
    no, you've missed out the dx, which you need to write in the form f(u)du :redface:

    (you could try using (cos2x + sin2x)2, but i don't see how to finish that :frown:)
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