cos(八分之π-α）=三分之根号三,则sin(α-六分之π）的平方-cos(六分之5π+α）的值 帮我下
问题描述：
cos(八分之π-α）=三分之根号三,则sin(α-六分之π）的平方-cos(六分之5π+α）的值 帮我下
答
∵cos（π/8-α）=√3/3 ∴π/8-α=±π/6+2kπ,k∈Z α=7π/24+2kπ或-π/24+2kπ,k∈Z 当α=7π/24+2kπ时,原式=sin^2（7π/24+2kπ-π/6）-cos（5π/6+7π/24+2kπ） =sin^2π/8-cos9π/8 =sin^2π/8+cosπ/8 =1-...