Let . From the diagram below, we see that the reference angle here is . Hence, we are working with a 30°- 60°- 90° triangle positioned in Quadrant II in the following way:
From this we can see the following:
. From the diagram below, we see that the reference angle
here is 
. Hence, we are working with a
![[diagram]](p8-5.gif)
![[trig values for 150 degrees]](img74.gif)