cos5/12πcosπ/12+cosπ/12sinπ/6=?
问题描述：
cos5/12πcosπ/12+cosπ/12sinπ/6=?
答
cos5/12πcosπ/12+cosπ/12sinπ/6=cosπ/12（cos5/12π+sinπ/6）=cosπ/12（cos(π/2-π/12)+sinπ/6）=cosπ/12（sin(π/12)+2*sin(π/12)*cos(π/12))=sin(π/12)*cos(π/12)*（1+2*cos(π/12))=1/2*sin(π/6)*...