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Reverse the order of integration

  1. Apr 15, 2010 #1
    why sometime we need to reverse the order of integration?
    and how to determine the new limit?
    for example: for integration of dydx, the limit of y and x:
    y=2x , y=2;
    0<=x<=1.
    after we reverse the order become dxdy, how to determine the new limit of x and y?
     
  2. jcsd
  3. Apr 15, 2010 #2

    LCKurtz

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    You use the picture to get the limits going in the x direction first, just like you would use the picture going in the y direction first for the dydx integral.
     
  4. Apr 15, 2010 #3
    erm..draw de picture..
    how about if i don't know how to draw it?
    can teach me any method to find the new limit?
     
  5. Apr 15, 2010 #4

    LCKurtz

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    Draw the graph of y = 2x and y = 2 for x between 0 and 1. It should form a triangle with the y axis. That's the region in question. You know how to do that, right?
     
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