Ответ:

x=π*k

x=(-2/3)π+2πk

x=(2/3)π+2πk

Объяснение:

f'(x)=-sin(x)-2cos(x)*sin(x)=-sin(x)(1+2cos(x))=0

sin(x)=0 => x=π*k

1+2cos(x)=0 => cos(x)=-1/2

x=-(2/3)π+2πk

x=(2/3)π+2πk