SOLUTION: if cos x = 1/9 and x is an obtuse angle, find sin 1/2 x

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Question 843989: if cos x = 1/9 and x is an obtuse angle, find sin 1/2 x
Answer by lwsshak3(11628) About Me  (Show Source):
You can put this solution on YOUR website!
if cos x = 1/9 and x is an obtuse angle, find sin 1/2 x

sin(1/2)x=2/3 (in quadrant II where sin>0)
calculator check:
cos(x)=1/9 (in quadrant IV)
x=360-83.62≈276.38˚
x/2≈138.19˚
sin(x/2)=sin(138.19)≈0.6666..≈2/3