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Help in Solving a problem using F.T.C

  1. Sep 28, 2011 #1
    Hi, here's my problem

    Use the Fundamental Theorem of Calculus to evaluate the definite integral.
    from the int. of -1 to 1, with the function being 5/x^2+1

    = 5 int. 1/x^2+1
    = 5 int. tan^(-1)(x)
    = 5 x tan^-1(x)
    Plug in 1 and -1...subtract...= 450, except it's wrong.

    I've gotten as far as 5 int. tan^-1(x), and I get 450 once I plug in the limits, Am I missing anything?
  2. jcsd
  3. Sep 28, 2011 #2


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    You need parentheses if you mean an integrand of 1/(x2+1)
    And if you have taken the antiderivative, you shouldn't still have the "int" in front.
    And where did the x in front come from?

    That last antiderivative, somehow, is actually correct. But remember in derivatives and integrals of trig function, x is always in radians.
  4. Sep 28, 2011 #3
    excellent, got it.

    Thanks a million.
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