Saturday, 12 April 2014

integration - What did I do wrong in calculating intinftyinftyfracsinxxmathrmdx via ointgammafracsinzzmathrmdz?

I tried to calculate the sinxxdx by the complex integral γsinzzdz, where γ is the half-circle with y>0.



sinxxdx={γeizzdz}={2πiRes[eizz,0]}={2πilim
Now, I know the integral \int_{-\infty}^{\infty}\frac{\sin{x}}{x}\mathrm{d}x = \pi by many other theorems.
So, what did I do wrong?



If you know, can you please write the correct answer? Thanks!

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