SOLUTION: If sin x = -(4/5) and x is in quadrant IV, find cos (1/2) x

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Question 449671: If sin x = -(4/5) and x is in quadrant IV, find cos (1/2) x
Answer by lwsshak3(11628) About Me  (Show Source):
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If sin x = -(4/5) and x is in quadrant IV, find cos (1/2) x
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We are working with a 3-4-5 right triangle in quadrant IV where sin is negative and cos is positive.
Cos x=3/5
Using the half-angle formula for cosine,
cos x/2=sqrt((1+cos x)/2)
=sqrt((1+3/5)/2
=sqrt((8/5)/2
cos x/2 =√.8 (ans)