## Precalculus (6th Edition)

$r=8$ units
The radius of the circle can be found using the formula for the length of arc (s), which is $s=r\theta$. Substitute the given values of $\theta$ and $s$ to obtain: $s=r\theta \\6\pi=r(\frac{3\pi}{4}) \\\frac{4}{3\pi} \cdot 6\pi=r(\frac{3\pi}{4})\cdot (\frac{4}{3\pi})$ $\\8=r$ units