也就是说，单位长度等于半径。

So, take the length unit to be equal to the radius.

youdao

是一个半径为1的圆，那是单位圆。

That is a circle of radius 1. That's the unit circle.

youdao

是一个半径为1的圆，那是单位圆。

That is a circle of radius 1. That's the unit circle.

youdao