sin(π/16)^2-cos(π/16)^2
问题描述：
sin(π/16)^2-cos(π/16)^2
答
sin(π/16)^2-cos(π/16)^2
=-cosπ/8
=-√[(1+cosπ/4)/2]
=-√[(1+√2/2)/2]
=-√(2+√2)*1/2