Giacomo Prando summarizes the troubled history of the radian, a unit with the odd property of appearing and disappearing seemingly at will in dimensional formulas.

中文翻译：

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光谱单位

贾科莫·普兰多（Giacomo Prando）总结了弧度的困扰历史，弧度是一个在维数公式中具有随意出现和消失的奇怪特性的单元。