#### Answer

If a radius with a length of $r$ units rotates through an angle of 1 radian, then the arc length is $r$ units. An angle of 1 radian subtends an arc length that is equal to the radius.

#### Work Step by Step

Radian measure is a unit that is used to measure an angle.
If a radius with a length of $r$ units rotates through an angle of 1 radian, then the arc length is $r$ units. An angle of 1 radian subtends an arc length that is equal to the radius.
We can use the conversion factor $\frac{180^{\circ}}{\pi}$ to convert from radians to degrees.
$(1~radian) \times \frac{180^{\circ}}{\pi} = 57.3^{\circ}$
An angle of 1 radian is equal to $57.3^{\circ}$