已知cos(π/6-α)=m(|m|≤1),求cos(5π/6+α),sin(2π/3-α)的值
问题描述：
已知cos(π/6-α)=m(|m|≤1),求cos(5π/6+α),sin(2π/3-α)的值
答
∵cos(π/6-α)=m(|m|≤1),
∴cos(5π/6+α)
=cos[π-(π/6-α)]
=-cos(π/6-α)
=-m
sin(2π/3-α)
=sin[π/2+(π/6-α)]
=cos(π/6-α)
=m