CVD2

From Exampleproblems

Find $\frac{d}{dz}\left[\frac{1+z}{1-z}\right]\,$ .

$\frac{d}{dz}\left[\frac{1+z}{1-z}\right]=\lim_{\Delta z \rightarrow 0}\frac{\left(\frac{1+z+\Delta z}{1-z-\Delta z}\right)-\left(\frac{1+z}{1-z}\right)}{\Delta z}=\lim_{\Delta z \rightarrow 0}\frac{(1-z)(1+z+\Delta z)-(1+z)(1-z-\Delta z)}{\Delta z(1-z-\Delta z)(1-z)}\,$