- #1
bwinter
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Homework Statement
The question asks that you prove that
[tex]\int\frac{sin^{2}x}{x^2}dx = \pi / 2[/tex]
The integral is from zero to infinity, but I don't know how to add those in latex.
Homework Equations
Use a contour integral to get around the pole at z = 0. The problem is, I'm really really foggy on how to do that. Professor says residue theorem doesn't need to be used--and besides, isn't the residue at z = 0 just 0 anyway?
The Attempt at a Solution
Integrate around it by subtracting out a small circular contour around the pole, and then adding it back in.
First, I converted the integral to complex form, and changed the boundaries to -inf to inf, by multiplying by one half. I know this much is right.
[tex]Re \left\{\frac{1}{2} \int\frac{e^{i2z}-1}{z^2}dz\right\}[/tex]
Then I integrate around a small contour: but am I doing this right? Do I just sub these in?
[tex]z = \epsilon e^{i\theta}[/tex] and [tex]dz = i\epsilon e^{i\theta}d\theta[/tex]. Bounds of the integral should be from [tex]\pi[/tex] to 0 if I'm integrating above. Then what? I'm lost. Any integral I try to solve from then on just gives me 0. And what do I do about the exponential in the exponential? I've never seen e to the e before and I don't know what to do with it when integrating, which makes me question whether I'm doing this whole contour thing right. Help!
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