3sin2x+sinx*cosx=2cos2x

(sin (x)) ^3 - sin (x) - cos (x) = 0

sin (x) * ((sin (x)) ^2 - 1) - cos (x) = 0

sin (x) * ((1 - (cos (x)) ^2) - 1) - cos (x) = 0

sin (x) * (cos (x)) ^2 + cos (x) = 0

cos (x) * (sin (x) * cos (x) + 1) = 0

sin (x) * cos (x) = - 1

0.5 * sin (2*x) = - 1

sin (2*x) = - 2

решения нет

остается:

cos (x) = 0