TeX Quellcode:

\begin{array}{rcl}z_1\cdot z_2 &=& 3\left(\cos\left(\dfrac{\pi}{3}\right)+i\sin\left(\dfrac{\pi}{3}\right)\right)\cdot\dfrac{1}{4}\left(\cos\left(\dfrac{5\pi}{9}\right)+i\sin\left(\dfrac{5\pi}{9}\right)\right) \\ \\ &=& 3\cdot \dfrac{1}{4}\left(\cos\left(\dfrac{\pi}{3}+\dfrac{5\pi}{9}\right)+i\sin\left(\dfrac{\pi}{3}+\dfrac{5\pi}{9}\right)\right) \\ \\ &=& \dfrac{3}{4}\left(\cos\left(\dfrac{8\pi}{9}\right)+i\sin\left(\dfrac{8\pi}{9}\right)\right)\end{array}