SOLUTION: find exact value cos (-15 degrees)

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Question 953691: find exact value
cos (-15 degrees)
Answer by lwsshak3(11628) About Me  (Show Source):
You can put this solution on YOUR website!
find exact value
cos (-15 degrees)=cos(45-60)
=cos45cos60+sin45+sin60=√2/2*1/2+√2/2*√3/2=√2/4+√6/4=(√2+√6)/4
Check:
cos(-15˚)≈0.9659
Exact value as computed=(√2+√6)/4≈0.9659