Question

已知OA上向右箭头=(sin3分之x,根号3cos3分之x),OB上向右箭头=(cos3分之x,cos3分之x)(x属于

Answer 1

解析：F(x)=向量OA?向量OB =1/2*sin(2x/3)+√3(cos(x/3))^2=1/2*sin(2x/3)+√3/2*cos(2x/3)+ √3/2

F(x)=sin(2x/3+π/3)+√3/2

F(x)的一条对称轴为：(2x/3+π/3)=π/2==>2x/3=π/6==>x=π/4