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Homework Help: Integrattion problem

  1. Sep 21, 2010 #1
    1. The problem statement, all variables and given/known data
    integral of cos^2 * (sqr(1+tan^2))

    2. Relevant equations

    3. The attempt at a solution
    let u = 1 +tan^2
    du = sec^2

    im not sure how 1/cos^2 gets accounted for the cos^2 in the front
  2. jcsd
  3. Sep 21, 2010 #2


    User Avatar
    Homework Helper

    You did your differentiation wrong. In fact you don't need to use substitution. Firstly what is 1+tan^{2}x?
  4. Sep 21, 2010 #3


    Staff: Mentor

    If u = 1 + tan^2(theta), du = 2tan(theta)*sec^2(theta)d(theta)

    In any case, this is not a good substitution to use.

    There are some trig identities that can be used to simplify the integrand first, and then the integration is very simple.
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