Cauchy-Riemann Equations

jeff-844

hey,
I am in the process of solving a problem regarding Cauchy-Riemann equations.I am stuck on a part where I have to integrate (x^2-y^2)/(x^2+y^2)^2.I am thinking that I should substitute x for tan t to solve it but it isn't working out for me.Could someone help me by solving this for me as I can't afford the time to be working out integrals cause I have an exam in a weeks time.Any help would be much appreciated.Thanks.