sin13°+cos30°sin17°/cos13°-sin30°sin17°化简求值
问题描述：
sin13°+cos30°sin17°/cos13°-sin30°sin17°化简求值
答
13°=30°-17°
sin13°=sin(30°-17°)=sin13cos17-cos13sin17
cos13°=cos(30°-17°)=cos13cos17+sin13sin17
则sin13°+cos30°sin17°/cos13°-sin30°sin17°
=sin13cos17/cos13cos17°
=tan13°
答
（sin13度＋sin17度×cos30度）/(cos13度－sin17度×sin30度)
=（sin(30-17)度＋sin17度×cos30度）/(cos(30-17)度－sin17度×sin30度)
=sin30度cos17度/cos30度cos17度
=tan30度
=√3/3