名詞 radian:

1. the unit of plane angle adopted under the Systeme International d'Unites; equal to the angle at the center of a circle subtended by an arc equal in length to the radius (approximately 57.295 degrees)
   同義詞：rad

ra.di.an

n.Abbr. radMathematics （名詞）縮寫 rad【數(shù)學(xué)】
A unit of angular measure equal to the angle subtended at the center of a circle by an arc equal in length to the radius of the circle, approximately 57=7&S{￠}44.'".See table at measurement
弧度：平面角的一種衡量單位，其大小為長度等于半徑的弧對的圓心角，弧度角約等于57=7&S{￠}44.'"參見 measurement

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radi(us)
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