\frac{z_1}{z_2}=|\frac{z_1}{z_2}|\:\left\lbrack\cos\left(\alpha_1-\alpha_2\right)+\sin\left(\alpha_1-\alpha_2\right)\right\rbrack
\frac{\cos\:\frac{15\pi}{4}+i\:\sin\:\frac{15\pi}{4}}{2\sqrt3\left(\cos\:\frac{11\pi}{4}+i\:\sin\:\frac{11\pi}{4}\right)}
\large =\Large \frac{\sqrt {3}}{6}\large \left( \cos {\frac{\pi}{4}}+\text{i}\sin {\frac{\pi}{4}}\right)