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Changing the function w.r.t in integration

  1. Aug 3, 2014 #1
    How to change the function w.r.t we are doing integration(function other then x) .what does it mean to do so.
  2. jcsd
  3. Aug 4, 2014 #2


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    It's not clear what you are asking. Can you provide an example of what you are trying to do?
  4. Aug 4, 2014 #3


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    Do you mean, for example, [itex]\int x du[/itex] where [itex]u= x^2[/itex]? In that case [itex]du= d(x^2)= 2xdx[/itex] so the integral becomes [itex]\int x (2x dx)= 2\int x^2 dx[/itex].

    In general, [itex]\int f(x) dg(x)= \int f(x) g'(x)dx[/itex] because [itex]dg(x)= g'(x)dx[/itex].
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