\(9-4i\\ r = \sqrt{9^2+(-4)^2} = \sqrt{97} \\ \alpha = tan^{-1}(\frac{-4}{9}) \Leftrightarrow \alpha =156^\circ 2' 15"\text{ of } \alpha = 336^\circ 2' 15"\\9-4i\text{ ligt in kwadrant }4, \alpha \text{ ligt dus tussen }270^\circ \text{ en }360^\circ\\ \alpha = 336^\circ 2' 15"\)