None A B C D E F None Solution2cos24theta1 cos2 4theta12 cos

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Solution

2cos²4theta=1

cos² 4theta=1/2

cos 4theta=+-1/sqrt2

4 theta= cos^-1(+-1/sqrt2)

4theta=pi/4/ 3pi/4,5pi/4,7pi/4/ 9pi/4,11pi/4,13pi/4/15pi/4,17pi/4,19pi/4,21pi/4,23pi/4,25pi/4,27pi/4,29pi/4,31pi/4

theta=pi/16,3pi/16,5pi/16,7pi/16,9pi/16,11pi/16,13pi/16,15pi/16,17pi/16,19pi/16,21pi/16,23pi/16,25pi/16,27pi/16,29pi/16,31pi/16