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