Question

sin13°+cos30°sin17°/cos13°-sin30°sin17°化简求值

Answer 1

（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

Answer 2

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°