How do you reduce $H\left(e^{j\frac{\pi}{2}}\right)$ further according to a textbook solution I want to know how I could get from the first line to the second. I've been trying to figure it out for a while with no luck. Thank you in advance!
\begin{align}
H\left(e^{j0.5\pi}\right) &amp;= \frac{1 - e^{-j0.5\pi}}{1 - 0.25e^{-j\pi}}\\
&amp;=1.13e^{j\frac{\pi}{4}}
\end{align}
By plotting the unit circle you will find that $1-e^{-j\pi/2} = \sqrt{2}e^{j\pi/4}$.