cos20°-cos40°+cos60°+cos100°的值等于 _．
问题描述：
cos20°-cos40°+cos60°+cos100°的值等于 ______．
答
cos20°-cos40°+cos60°+cos100°
=cos（60°-40°）+cos（60°+40°）-cos40°+cos60°
=2cos60°cos40°-cos40°+cos60°
=cos60°
=
1 2
故答案为：
1 2