cos1°+cos2°+cos3°+...+cos179°化简
人气：307 ℃ 时间：2020-02-02 20:09:37
解答
cos1°=-cos179°
同理,cos2°=-cos178°,cos3°=-cos177°
则cos1°+cos179°=0
原式可简化为0+cos90°=0
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