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)= .
sin(210)= sin(180+ 30)= sin(30)=
cos(135)= cos(90+ 45)= -cos(45)=
sin(135)= sin(90+ 45)= sin(45)=
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)?