问题描述: 若角α为锐角,且sin(a-π/6)=1/3,则cosα=? 1个回答 分类:数学 2014-10-14 问题解答: 我来补答 sin(a-π/6)=1/3cos(a-π/6)=√[1-sin^2(a-π/6)]=√(1-1/9)=2√2/3sinacosπ/6-cosasinπ/6/2sina-1/2cosa=1/3cosα=(a-π/6+π/6)=cos(a-π/6)cosπ/6-sin(a-π/6)sinπ/6=(2√2/3)*(√3/2)-(1/3)*(1/2)=(2√6-1)/6 展开全文阅读