# What is the trigonometric form of  (-9-2i) ?

$Z = \sqrt{85} \left(\cos 3.36 + i \sin 3.36\right)$
$r = \sqrt{{2}^{2} + {9}^{2}} = \sqrt{85}$ This is in 3rd quadrant. $\angle \alpha = {\tan}^{-} 1 \left(\frac{2}{9}\right) = .22 r a d \therefore \theta = 3.14 + .22 = 3.36 r a d$ So in trigonometric form $Z = \sqrt{85} \left(\cos 3.36 + i \sin 3.36\right)$[ans]