机器战警动画片:高一数学题(三角函数)

来源:百度文库 编辑:高考问答 时间:2024/03/28 16:46:27
求值cos20°+cos60°+cos100°+cos140°
cos40°+cos60°+cos80°+cos160°
题目中间换行表示这是两个题,请帮忙分别解答,谢谢

1

cos20°+cos60°+cos100°+cos140°+
cos40°+cos60°+cos80°+cos160°
=(cos20°+cos160°)+(cos140°+cos40°)+(cos100°+cos80°)+2cos60°
=2*1/2=1