sin(a-π/3)=1/3,则cos(π/6+a)的值为___
问题描述：
sin(a-π/3)=1/3,则cos(π/6+a)的值为___
答
cos(π/6+a)=sin[π/2-(π/6+a)]=sin(π/3-a)= - sin(a-π/3)= -1/3
sin(a-π/3)=1/3,则cos(π/6+a)的值为___
cos(π/6+a)=sin[π/2-(π/6+a)]=sin(π/3-a)= - sin(a-π/3)= -1/3