Paper 2, Section II, B

Complex Analysis or Complex Methods
Part IB, 2015

(i) A function f(z)f(z) has a pole of order mm at z=z0z=z_{0}. Derive a general expression for the residue of f(z)f(z) at z=z0z=z_{0} involving ff and its derivatives.

(ii) Using contour integration along a contour in the upper half-plane, determine the value of the integral

I=0(lnx)2(1+x2)2 dxI=\int_{0}^{\infty} \frac{(\ln x)^{2}}{\left(1+x^{2}\right)^{2}} \mathrm{~d} x