Example: Determine the radius of a circle given an arc length of \(12\) cm is subtended by an angle of 3 radians.
Solution This solution follows right along the arc length formula: \(s=r\theta\), but this time we use the arc length to find the radius:
\[ \solve{12&=&r\times 3\\ 4&=&r }\]Thus, the radius of this circle must be 4 centimeters.