高一数学三角函数请详细解答,谢谢!(420:57:55)
若sin(3兀+乄)=1/4,求cos(兀+乄)/cos乄[cos(兀+乄)-1]+cos(乄-2兀)/[cos(乄+2兀).cos(乄+兀)+cos(-乄)]的值.