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Improper integrals and canceling of areas

  1. Mar 31, 2013 #1
    When evaluating an improper integral and i get infinity minus infitiy when taking the limit. in what case do the areas cancel?
  2. jcsd
  3. Mar 31, 2013 #2


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    Infinity minus infinity is not equal to zero. You have a divergent integral.
  4. Mar 31, 2013 #3


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    In general, no. If f has, for example, a singularity at x= b, where a< b< c, then [tex]\int_a^c f(x)dx= \lim_{\alpha\to b}\int_a^\alpha f(x)dx+ \lim_{\beta\to b}\int_\beta^c f(x)dx[/tex].

    Those two limits have to be taken independently so you cannot cancel them.
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