题目

设α为钝角,若sin(α+π/6)=1/3 则cos(2α+π/12)=?

提问时间：2021-01-15

答案

cos(2α+π/12)=cos(α+π/6+α+π/6-π/4)=cos(α+π/6)cos(α+π/6-π/4)-sin(α+π/6)sin(α+π/6-π/4)=(-2/3)√2cos(α+π/6-π/4)-1/3sin(α+π/6-π/4)=(-2/3)√2[cos(α+π/6)cosπ/4+sin(α+π/6)sinπ/4]-...