# CVR15

Find the residues of $f(z)\,$ at all its isolated singular points and at infinity (if infinity is not a limit point of singular points), where $f(z)\,$ is given by $\frac{\sin z}{z^2+4}\,$

The poles are at $z=\pm2i\,$.

$\lim_{z\to 2i} \frac{\sin z}{z+2i} = \frac{\sin 2i}{4i} = \frac{\sinh 2}{4}\,$

$\lim_{z\to -2i} \frac{\sin z}{z-2i} = \frac{\sin -2i}{-4i} = \frac{\sinh 2}{4}\,$

##### Toolbox

 Get A Wifi Network Switcher Widget for Android