\(-10+5i\\ r = \sqrt{(-10)^2+5^2} = \sqrt{125} \\ \alpha = tan^{-1}(\frac{5}{-10}) \Leftrightarrow \alpha =153^\circ 26' 5{,}8"\text{ of } \alpha = 333^\circ 26' 5{,}8"\\-10+5i\text{ ligt in kwadrant }2, \alpha \text{ ligt dus tussen }90^\circ \text{ en }180^\circ\\ \alpha = 153^\circ 26' 5{,}8"\)