A radian is the Angle subtended by an arc of a circle whose length is just equal to the radius.

一弧度就是长度刚好等于半径的一段圆弧所对的圆心角。

youdao

A radian is the Angle subtended by an arc of a circle whose length is just equal to the radius.

一弧度就是长度刚好等于半径的一段圆弧所对的圆心角。

youdao