What reference angle in the first quadrant corresponds to theta = -120? answer in radians.

To draw theta=-120° in the unit circle, we move clockwise 90°, then another 30°.

This means that we pass the fourth quadrant and stop in the third quadrant.

The reference angle of an angle theta in the third quadrant, is theta + 180°.

So the reference angle of -120° is -120°+180°=60°.

         360° are 2π Radians
then  60° are 1/6 of 2π Radians = π/3 Radians

Reference angle is π/3 Radians