Answer
$\tan$ -1020$^{\circ}$ = $\sqrt3$
Work Step by Step
$\cos$ -1020$^{\circ}$
First, lets find the coterminal angle.
-1020$^{\circ}$ - 3(360$^{\circ}$) = 60$^{\circ}$
Next, we find the reference angle.
$\theta$$^{1}$ = 60$^{\circ}$
Since the coterminal angle is in Quadrant I, $\tan$ is negative.
Therefore:
$\tan$ 60$^{\circ}$ = $\sqrt3$