cos(π/6-a)=三分之根号三,sin²（a-π/6）=?

题目

cos(π/6-a)=三分之根号三,sin²（a-π/6）=?

答案

cos(π/6-a)=√3／3,则cos(a-π/6)=√3／3,sin²（a-π/6）=1-cos²（a-π/6)=2／3