An arc is a portion of the circumference of a circle.
Radius is the distance from the centre of the circle to its circumference.
From the formula to calculate the length of an arc;
![Calculate Radius of an Arc.](https://www.learntocalculate.com/wp-content/uploads/2020/04/Arc-length-1.png)
We get;
![Calculate Radius of an Arc.](https://www.learntocalculate.com/wp-content/uploads/2020/04/An-arc-length.png)
Example:
Calculate the radius of an arc length whose length is 9cm and the angle between the radii is 50 degrees.
![Calculate Length of an Arc](https://www.learntocalculate.com/wp-content/uploads/2020/04/An-arc-length-2.png)
Therefore, the radius of the arc is 10.31 cm.