1. The problem statement, all variables and given/known data Find Poles & eval resides at those points for f(z) = sin(z)/(z^2+1) 2. Relevant equations I'm using Res f(z) = [g^m-1 (z_0)] / (m-1)! 3. The attempt at a solution So I worked out the f(z) = 1/(z-i) so g(z) = sin(z) /(z+i) for my first one did the sub for z=i and got sin(i)/2i But the working out (i'm working on past papers so I have the worked solutions, just not very detailed) The next line shows; = 1/4(e-(1/e)) What one earth don't I know about sin that gets to this point??