Answer: 

Explanation:
 The formula for calculate the arc lenght is:
 

 Where "r" is the radius and "
 " is the central angle of the arc in degrees.
" is the central angle of the arc in degrees.
 The formula used to find the circumference of a circle is:
 

 Where "r" is the radius.
 Then, we can observe that the formula for calculate the arc lenght can be rewritten in this form:
 

 Where "C" is the circumference of the circle.
 Finally we need to substitute the central angle and the circumference into 
 . Then the result is this:
. Then the result is this:
 
