3−sin70°2−cos210°=_．
问题描述：
=______． 3−sin70° 2−cos210°
答
=3−sin70° 2−cos210°
=3−sin70° 2−
1+cos20° 2
=2(3−sin70°) 3−cos 20°
=22(3−cos20°) 3−cos 20°
故答案为：2