Answer
$120^\circ$
Work Step by Step
1. As $\vec i$ represents the x-axis, for $\vec v=-i+\sqrt 3j$ (quadrant II), the angle with x-axis is given by $tan\theta=\frac{\sqrt 3}{-1}=-\sqrt 3$
2. Thus, we can get $\theta=tan^{-1}(-\sqrt 3)=120^\circ$ (quadrant II)
