题干

把两根硬纸条的一端钉在一起,转动其中一根纸条,可以得到大小不同的角。下图中的角各是什么角?它们有什么特点?

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答案(点此获取答案解析)

解:当两根硬纸条钉成的活动角转到两条边成一直线时,这样的角是平角。当一条边围绕着顶点转一周后和另一条边重合时,这样形成的角是周角。平角的两条边成一条直线,周角的两条边重合在一起。平角是180°,周角是360°。

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