SOLUTION: use double angle formulas to find exact value: SIN 660 degrees COS 240 degrees

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Question 923478: use double angle formulas to find exact value:
SIN 660 degrees
COS 240 degrees
Answer by lwsshak3(11628) About Me  (Show Source):
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use double angle formulas to find exact value:
SIN 660 degrees
COS 240 degrees
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sin2x=2sinxcosx
sin660˚=sin(2*330)=2sin330cos330=2*-√3/2*1/2=-2√3/4=-√3/2
..
cos2x=cos^2(x)-sin^2(x)
cos240˚=cos^2(120)-sin^2(120)=1/4-3/4=-2/4=-1/2