Answer
$tan120^\circ=-1$
Work Step by Step
We are given $\tan120^\circ$
We can find the value by using right-angled triangle create by x, y, r and $\theta=60^\circ$
From the $30^\circ-60^\circ-90^\circ$ we will have $x=-1, y=1, r=1$
Using the definitions of the trigonometric functions give the following result
$tan120^\circ=-1$
