Solution
= Solution
The principal <complex exponentiation> gives $z^i=e^{-\theta}e^{i\log r}$. Equality to one requires its <complex modulus> to be one, hence $\theta=0$, and then its <complex argument> requires $\log r\in2\pi\mathbb Z$. Thus \b[all solutions are positive real], namely
$$
\boxed{z=e^{2\pi k},\qquad k\in\mathbb Z.}
$$
Substitution verifies every value, and the modulus condition excludes every nonreal value.