i^{1/2}
and
z^{1/n and }
-9
where z=x+i y
$\displaystyle \displaystyle \begin{align*} i^{\frac{1}{2}} &= \left( e^{i \frac{\pi}{2}} \right)^{\frac{1}{2}} \\ &= e^{i \frac{\pi}{4}} \end{align*}$
and
$\displaystyle \displaystyle \begin{align*} z^{\frac{1}{n}} &= \left( r\, e^{i\theta} \right)^{\frac{1}{n}} \\ &= r^{\frac{1}{n}}\,e^{i\frac{\theta}{n}} \end{align*}$
and
$\displaystyle \displaystyle -9 = 9\,e^{ i \pi } $