Trigonometry
posted by Jennifer .
use the appropriate trig identity (sum and difference, half angle, double angle) to find the exact value. 1)cos 255 degrees
2) sin 165 degrees
3) tan 285 degrees

isn't 255 = 180+75=27015 which is 27030/2?
isn't 165=18030/2
isn't 285=270+30/2?