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Math Help - Simple integration please help

  1. #1
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    Simple integration please help

    Integrate x + pi dx between pi and -pi

    thanks
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  2. #2
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    Quote Originally Posted by adam_leeds View Post
    Integrate x + pi dx between pi and -pi
    If you want help with a calculus problem, don't put it in the pre-calculus section!

    So, what's the difficulty? The integral of x is \tfrac12x^2, the integral of \pi (being a constant) is \pi x. Add them together, evaluate the result at \pi and -\pi, and take the difference.
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  3. #3
    NRS
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    Well...

    To solve the integral, raise x to the second power and divide it by 2, and add an x to pi to get:

    (2x)/2 + pi(x) + C

    Now just solve the integral for pi to -pi, so you would just sub in and solve by subtracting the second number solved in the indefinite integral, minus the first.

    ((2pi)/2 + pi(pi)) - ((2(-pi)/2 + pi(-pi))

    (4pi)/2 + 2(pi)^2
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  4. #4
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    Quote Originally Posted by NRS View Post
    To solve the integral, raise x to the second power and divide it by 2, and add an x to pi to get:

    (2x)/2 + pi(x) + C
    You just said "raise x to the second power" but now you write "2x"!
    That should be x^2/2+ pi x+ C

    Now just solve the integral for pi to -pi, so you would just sub in and solve by subtracting the second number solved in the indefinite integral, minus the first.

    ((2pi)/2 + pi(pi)) - ((2(-pi)/2 + pi(-pi))

    (4pi)/2 + 2(pi)^2
    And apparently that was not just a typo since you now calculate 2 times pi rather than squareing. You should have
    (pi)^2/2+ pi(pi)- ((-\pi)^2/2- pi(-pi))= 2pi^2
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  5. #5
    NRS
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    Sorry, I must have made the typo, then calculated according to it. Should do better checking my work, sorry.
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