Subtract full rotations of until the angle is greater than or equal to and less than .

Apply the reference angle by finding the angle with equivalent trig values in the first quadrant. Make the expression negative because cosine is negative in the second quadrant.

The exact value of is .

Subtract full rotations of until the angle is greater than or equal to and less than .

Apply the reference angle by finding the angle with equivalent trig values in the first quadrant.

The exact value of is .

Set up the coordinates .

Find the Value Using the Unit Circle (8pi)/3