SOLUTION: solve cos15 without using calculater

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Question 435392: solve cos15 without using calculater
Answer by lwsshak3(11628) About Me  (Show Source):
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solve cos15 without using calculater
use cos 1/2 angle formula:
cos s/2=+-sqrt((1+cos s)/2)
cos15=cos(30/2)=(sqrt(1+cos30)/2)
sqrt((1+sqrt(3)/2)/2)
sqrt(2+sqrt(3)/2 (Note: solution positive because cos 15 in quad I is positive)