5. Let the sequences $\left\{x_{n}\right\},\left\{y_{n}\right\}$ satisfy $x_{n}+i y_{n}=\left(\frac{\sqrt{3} i-1}{2}\right)^{n}$, find the sum of the first 1994 terms of the sequence $\left\{x_{n}\right\}$, $S_{1994}$.
5. Let $F=x_{n}+i y_{n}=\left(\frac{\sqrt{3} i-1}{2}\right)^{n}, \quad F^{\prime}=x_{n}-i y_{n}=\left(\frac{-\sqrt{3} i-1}{2}\right)^{n}$, then $F+F^{\prime}=2 x_{n}=\omega^{n}+\bar{\omega}^{n}$. (where $\omega=\frac{-1+\sqrt{3} i}{2}$ ). Thus $2 S_{1994}=-2$, which means $S_{1994}=$ $-1$