（tan5°-cot5°）×cos70°1+sin70°=_．
问题描述：
（tan5°-cot5°）×
=______． cos70° 1+sin70°
答
（tan5°-cot5°）×
=（cos70° 1+sin70°
-sin5° cos5°
）•cos5° sin5°
sin20° 1+cos20°
=
•
sin25°−cos25° sin5°cos5°
=sin20° 1+cos20°
•−cos10°
sin10°1 2
=-2，2sin10°cos10°
2cos210°
故答案为：-2．