The arc length is given by:
[tex]s=r\theta[/tex]
where the angle has to be in radians.
Then we have to transform the angle to radians. To do this we use the formula:
[tex]\theta\cdot\frac{\pi}{180}[/tex]
Then our angle in radians is:
[tex]30\cdot\frac{\pi}{180}=\frac{\pi}{6}[/tex]
Now that we have the angle we plug its value and the radius in the formula:
[tex]s=9\cdot\frac{\pi}{6}=\frac{3}{2}\pi[/tex]
Therefore the arc length is:
[tex]s=\frac{3}{2}\pi[/tex]
