3сos^2x-3cosx-2=0
cosx=t
3t^2-3t-2=0
t=[3+-sqrt(9+24)]/6=[3+-sqrt(33)]/6
[3+sqrt(33)]/6>1
[3-sqrt(33)]/6=sinx
x=arcsin(3-sqrt(33))+2Пk
проверяйте условие
3сos^2x-3cosx-2=0
cosx=t
3t^2-3t-2=0
t=[3+-sqrt(9+24)]/6=[3+-sqrt(33)]/6
[3+sqrt(33)]/6>1
[3-sqrt(33)]/6=sinx
x=arcsin(3-sqrt(33))+2Пk
проверяйте условие