f(x)=sin2x+acos2x关于直线x=-π/6对称
且,x属于R
所以f(-π/6-π/6)=f(-π/6+π/6)
f(-π/3)=f(0)
f(-π/3)=sin(-2π/3)+acos(-2π/3)=-(根号3)/2-a/2
f(0)=sin(0)+acos(0)=a
a=-(根号3)/2-a/2
a=-(根号3)/3