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

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