(sin10+sin20cos30)/(cos10-sin20sin30)=(sin10+（sin(20+30)+sin(20-30)）/2)/(cos10+(cos(20+30)-cos(20-30))/2)=(（sin(30+20)+sin(30-20)）/2)/((cos(20+30)+cos(20-30))/2)=（sin30cos20）/(cos20cos30)=sin30/...