Answer:
radians
Step-by-step explanation:
Arc length and radius is given. So, we need to know the arc length formula for a circle.
That is:

Where s is the arc length
r is the radius
is the angle (IN RADIANS)
We have:
s = 15.5
r = 9
Now, we substitute and find the angle:

The angle, in radians, in 1.72