The formula we'll use is
s = r*theta
where,
s = arc length
r = radius
theta = angle in radians
In this case,
r = 16 inches
theta = pi/4 radians
So this means,
s = r*theta
s = 16*(pi/4)
s = 4pi
The arc is exactly 4pi inches long.
Since the "pi" part is taken care of already, you just need to enter a whole number. In this case, you would enter 4 into the box.
