To find the value of sine and cosine at non-acute angles (from
90 to 360), first draw the angle on the unit circle and find the
reference angle. A reference angle is formed by the terminal
side and the x-axis and will therefore always be acute. When
evaluating cosine and sine for the reference angle, determine if
each value is positive or negative by identifying the quadrant
the terminal side is in. Okay I want to talk about how to find
the sine and cosine of angles that aren't acute, so I'm going to
start with an example finding the cosine and sine when theta
equals 150 degrees. And I've drawn theta here in standard
position so I need to find the coordinates of point q remember x
is going to be the cosine of 150 degrees and y is the sine. And
the trick to this is finding the reference angle. The reference
angle is the angle made by the terminal side of your angle and
the x axis and in this case it's 30 degrees and then you need to
find the cosine and sine of 30 degrees which by now we found and
the cosine of