Answer: tan -390 = (-√3)/3
Explanation:
In order to find your reference angle add 360 to the angle they give you.
-390 + 360 = -30
Your reference angle is 30°. Using a unit circle:
Where sin 30 = 1/2 and cos x = √3/2
Since we are looking at -30, in quadrant 4, you y/sin is -
sin -30 = -1/2 and cos -30 = √3/2
tan -30 = (sin -30)/(cos -30) >substitute
tan -30 = (-1/2)/(√3/2) >Keep change flip fractions
tan - 30 = (-1/2)*(2/√3) >simplifly
tan -30 = -1/√3 >get rid of root on bottom
tan - 30 = (-√3)/3
tan -390 = (-√3)/3