Monday, 5 October 2015

Using Complex contour integration calculate intinftyinftyfracsinxx+i




Using Complex contour integration calculate sinxx+idx . Use the form f(x)sin(αx)dx




Now I used the form f(x)sin(αx)dx and converted the integral to Img(eixx+idx) where the contour is the positive semi-circle around the origin from [R,R] as R



But then the only pole of the above integral is x=i, which is not in the above contour hence the value of the integral in the above contour is zero thus the value of the integral is zero . But the answer given in the text is not so



Could someone please calculate this integral


Answer




Hint: sinxx+idx=xsinxx2+1dxisinxx2+1dx



and you can easily apply Jordan's lemma on these guys and calculate the integrals from residue theorem.


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