Determine 2 positive and 2 negative principal angles for a terminal arm with a related acute angle of 20° in quadrant III.
A "positive" angle will be one for which you went around the unit circle anti-clockwise. A "negative" angle will be one for which you went backward around the circle, or clock-wise.
What is your book's definition of a "principal angle" as related to an angle of the sort provided by this exercise? When you reply, please include a clear listing of your work and reasoning so far.
Thank you!