设b=a+π/3.从sin(b)=sin(a+π/3)=1/4,可以得到cos(b)=cos(a+π/3)=[1-(1/4)^2]的开方=(根15)/4.则sin(a)=sin(b-π/3)=sin(b)cos(π/3)-cos(b)sin(π/3). 代入sin(b), cos(b), 以及sin(π/3)和cos(π/3)的值就可以...