Answer
$35.8$ cm
Work Step by Step
The formula to be used here is $s=r\theta$ where $s$ is the arc length, $r$ is the radius and $\theta$ is the angle in radians.
Substituting the values of $r=15.2$ cm and $\theta=\frac{3\pi}{4}$ radians into the formula and solving using a calculator:
$s=r\theta=15.2\times\frac{3\pi}{4}\approx35.8$ cm