Question

cos^2x = 2 cos2x решить​

Answer 1

Ответ:

${ \cos }^{2} (x) = 2 \cos(2x) \\ \cos ^{2} (x) = 2\cos ^{2} (x) - 2\sin ^{2} (x) \\ - \cos ^{2} (x) = 2 - 2\cos ^{2} (x) \\ \cos ^{2} (x) = 2 \\ \cos (x) = \sqrt{2 } \\ x = arccos( \sqrt{2} ) + 2\pi \: n$