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Homework Help: Integration qns

  1. Dec 5, 2008 #1
    The question asks me to integrate x^2 sin x dx and then use it to find the exact value of the integration of abs ( x^2 sin x dx) with upper limit of pi/2 and lower limit of -pi/2.

    I have found the integration of x^2 sin x dx which is -x^2 cosx + 2xsinX + 2 cosx + C

    but after putting in the upper limits and lower limits i get the answer 2pi, where have i gone wrong because my first part is correct but the second part is different from the answer given.
     
  2. jcsd
  3. Dec 5, 2008 #2

    HallsofIvy

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    Science Advisor

    For what values of x is x2 sin x positive and for what values of x is it negative? Remember that |a|= a if a is positive and |a|= -a if a is negative. You cannot just evaluate x2 cosx + 2xsinX + 2 cosx + C at -pi/2 and pi/2.
     
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