Originally Posted by
HallsofIvy The first thing I would do is go ahead and find those sines and cosines.
Assuming that the arguments are degrees:
cos(210)= cos(180+ 30)= -cos(30)= $\displaystyle -\sqrt{3}/2$.
sin(210)= sin(180+ 30)= sin(30)= $\displaystyle \frac{1}{2}$
cos(135)= cos(90+ 45)= -cos(45)= $\displaystyle -\sqrt{2}/2$
sin(135)= sin(90+ 45)= sin(45)= $\displaystyle \sqrt{2}/2$
cos(65) and sin(65) are the only ones that cannot be written in a simple form. Are you sure it wasn't sin(60) and cos(60)?