Coterminal angles are angles in standard position. Recall, a complete cycle is 360 degrees or 2pi
To find a positive and a negative angle coterminal with a given angle, we add or subtract 360 degrees or 2pi
The given angle is 9pi/6
Thus,
The negative angle is
9pi/6 - 2pi = - 3pi/6
The positive angle is
9pi/6 + 2pi = 21pi/6
Thus, the correct option is the third one
