Question 878802
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Hi,
tan = sin/cos = -(1/2)/(&#8730;3/2) = -1/(&#8730;3 =  -&#8730;3/3
3x = 150°   0r 3x = 330°
 x = 50°  0r x = 110°
(cosx, sinx) Unit Circle summary for Reference
<img src='http://img9.imageshack.us/img9/2032/mfpe.png'border='0'/></a>