TeX Quellcode:

{\dfrac{7}{5}\left(\cos\left(\dfrac{7\pi}{5}\right)+i\sin\left(\dfrac{7\pi}{5}\right)\right) \; \cdot \; \dfrac{20}{21}\left(\cos\left(\dfrac{21\pi}{20}\right)+i\sin\left(\dfrac{21\pi}{20}\right)\right) \; = \; \dfrac{7}{5} \cdot \dfrac{20}{21} \left(\cos\left(\dfrac{7\pi}{5}+\dfrac{21\pi}{20} \right)+i \sin\left(\dfrac{7\pi}{5}+\dfrac{21\pi}{20} \right) \right) \; = \; \dfrac{4}{3} \left(\cos\left(\dfrac{49\pi}{20}\right)+i \sin\left(\dfrac{49\pi}{20}\right)\right) \; = \; \dfrac{4}{3} \left(\cos\left(\dfrac{9\pi}{20}\right)+i \sin\left(\dfrac{9\pi}{20}\right)\right)}