Roots of Complex Number/Exponential Form/Principal Root

Definition
Let $z := r e^{i \theta}$ be a complex number expressed in exponential form, such that $z \ne 0$.

Let $n \in \Z_{>0}$ be a (strictly) positive integer. The principal $n$th root of $z$ is the value of $r^{1/n} e^{i \theta / n}$ such that:
 * $-\pi < \theta \le \pi$