solve cos(z/2)*(cos(x)^2*cos(y)+sin(x)^2)+cos(x)*sin(y)*sin(z/2)=cos(z/2), cos(x)*sin(y)*cos(z/2)) -cos(y)*sin(z/2)=sin(z/2), sin(x)*sin(y)*sin(z/2)+cos(z/2)*(sin(x)*cos(x)*cos(y)-sin(x)*cos(x))=0