Wednesday, April 12, 2017

complex analysis - Help with this indefinite integral using residues?


Question: How to evaluate this integral using residues0xsinx1+x2dx



I integrate over the entire real axis and dividing it by 1/2 since the integrand is even, and then I do the thing with the turning it into Im(feixdx)

and integrate over the upper half plane by finding the residues there, and there's only one, at i.


So I put it into the equation xeiz2x and get 12e, so I get when plugging that in


0xsinx1+x2dx=.5xsinx1+x2dx=.5Im[2πiRes(xeix1+x2;i)]=.5[Im(2πi12e)]=π2e


But the answer's positive.


What did I mess up on?

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