A drawing program makes a spiral of points in the complex plane. It starts at $z_{0} = 10$ and makes each new point by multiplying the previous one by $u = 0.9\,\mathrm{cis}(0.5)$, so $z_{n} = u\,z_{n - 1}$ for $n \ge 1$ and $z_{n} = 10 u^{n}$.