cos20°-cos40°+cos60°+cos100°的值等于 _．

题目

cos20°-cos40°+cos60°+cos100°的值等于 ______．

答案

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