问题描述: 若sin(π/6-α)=1/3 则cos(2π/3+2α)等于多少 1个回答 分类: 综合 2014-11-20 问题解答: 我来补答 答案:-7/9cos(2π/3+2α)=-cos(π-2π/3-2α)=-cos(π/3-2α)=-[1-2sin(π/6-α)^2]=-7/9 展开全文阅读