15 deg
sin (30/2)= sqrt [(1-cos 30)/2 ]
cos 30 = sqrt 3 /2
sqrt [ (1- sqrt 3/2)/2]
sqrt [ (2 - sqrt (3) ) /4 ]
= (1/2) sqrt (2 - sqrt 3)
Find the exact value of cos 375 degrees.
Answer: (sqrt6 + sqrt2)/4
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