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Comparison Theorem and Limits of integration

  1. Apr 8, 2013 #1
    1. The problem statement, all variables and given/known data

    Why is it that when using the comparison theorem my limits of integration must be from a constant value to infinity and not from negative infinity to infinity?

    For example ∫ x/(1+x^2) dx from -∞ to ∞
     
  2. jcsd
  3. Apr 8, 2013 #2

    jbunniii

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    Can you be more specific about what comparison theorem you are talking about?

    For your example, notice that if ##x \geq 1##, you can easily check that
    $$\frac{x}{1+x^2} \geq \frac{1}{2x}$$
    What does that tell you?
     
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