cosx/2 – sqrt(3)sinx/2+1=0
cos^2(x/4)-sin^2(x/4)-sqrt(3)*2*sin(x/4)*cos(x/4)+sin^2(x/4)+cos^2(x/4)=0
2cos^2(x/4)-2*sqrt(3)*sin(x/4)*cos(x/4)=0
cos^2(x/4)-sqrt(3)*sin(x/4)*cos(x/4)=0
1) cos(x/4)=0
x/4=pi/2+pi*n
x=2*pi+4*pi*n
2) cos(x/4)=sqrt(3)*sin(x/4)
cos(x/4)/sin(x/4)=sqrt(3)
ctg(x/4)=sqrt(3)
x/4=arcctg(sqrt(3))+pi*n
x/4=pi/6+pi*n
x=2*pi/3+4*pi*n