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outhsakotad
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contour integration problem--(sinx/x)^2
I am to evaluate the integral of (sinx/x)^2 from -infinity to +infinity.
I drew my contour as a large half circle in UHP, and this contour then includes the singularity at the origin.
Using a trig identity, I can rewrite sin^x : 0.5(1-cos(2x))
Since we're working in the UHP, I then rewrite the integral: Real part of 0.5*int((1-e^(2iz))/z^2)dz from -inf to +inf
There is a second order pole at the origin. The residue here is a-= 0.5*(d/dz){(z^2*(1-e^(2iz)))/z^2)} evaluated as z-->0, = 0.5*-2i*e^(2i*0)=-i.
Since the part enclosing the singularity is a half circle, the integral should be pi*i*a-=pi. But the answer is supposed to be pi/2.
I apologize for the lack of LaTeX. Could somebody please give me a hint as to what I'm doing wrong? Thanks.
Homework Statement
I am to evaluate the integral of (sinx/x)^2 from -infinity to +infinity.
Homework Equations
The Attempt at a Solution
I drew my contour as a large half circle in UHP, and this contour then includes the singularity at the origin.
Using a trig identity, I can rewrite sin^x : 0.5(1-cos(2x))
Since we're working in the UHP, I then rewrite the integral: Real part of 0.5*int((1-e^(2iz))/z^2)dz from -inf to +inf
There is a second order pole at the origin. The residue here is a-= 0.5*(d/dz){(z^2*(1-e^(2iz)))/z^2)} evaluated as z-->0, = 0.5*-2i*e^(2i*0)=-i.
Since the part enclosing the singularity is a half circle, the integral should be pi*i*a-=pi. But the answer is supposed to be pi/2.
I apologize for the lack of LaTeX. Could somebody please give me a hint as to what I'm doing wrong? Thanks.