SOLUTION: by using formula cos A = underroot 1+ 2 cos 2A upon 2 find the value of cos 30 it being given that cos 60= 1/2

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Question 984641: by using formula cos A = underroot 1+ 2 cos 2A upon 2 find the value of cos 30 it being given that cos 60= 1/2
Answer by srinivas.g(540) About Me  (Show Source):
You can put this solution on YOUR website!
cos+A=sqrt%28%281%2Bcos%282A%29%29%2F2%29
put A=30
then
Cos%2830%29=sqrt%28%281%2Bcos%2860%29%29%2F2%29
+cos%2830%29=sqrt%28%281%2B%281%2F2%29%29%2F2%29
cos%2830%29=+sqrt%28%283%2F2%29%2F2%29
cos%2830%29=+sqrt%283%2F4%29
cos%2830%29=sqrt%283%29%2F2