Answer
$\theta = 30^{\circ}, 330^{\circ}$
Work Step by Step
$-3~sec~\theta +2\sqrt{3} = 0$
$\frac{-3}{cos~\theta} = -2\sqrt{3}$
$\frac{cos~\theta}{-3} = \frac{1}{-2\sqrt{3}}$
$cos~\theta = \frac{\sqrt{3}}{2}$
$\theta = 30^{\circ}, 330^{\circ}$
