f(π/6+x)=f(π/6-x)
[(asin(π/6+x)+cos(π/6+x)]cos(π/6+x)=[(asin(π/6-x)+cos(π/6-x)]cos(π/6-x)
[a(1/2cosx+√3/2sinx)+√3/2cosx-1/2sinx](√3/2cosx-1/2sinx)=[a(1/2cosx-√3/2sinx)+√3/2cosx+1/2sinx](√3/2cosx+1/2sinx)
(√3-1)/2 a sinxcosx=√3sinxcosx
a=(2√3)/(√3-1)=3+√3