化简（tan10°-3）•cos10°sin50°=_．
问题描述：
化简（tan10°-
）•
3
=______． cos10° sin50°
答
∵tan10°-
=
3
−sin10° cos10°
=
3
=sin10°−
cos10°
3
cos10°
=−2sin(10°−60°) cos10°
2sin50° cos10°
∴（tan10°-
）•
3
=−cos10° sin50°
•2sin50° cos10°
=-2cos10° sin50°
故答案为：-2