The formula for determining the length of an arc is expressed as
length of arc = #/360 * 2 * pi * radius
where
# represents the central angle
From the information given
length of arc = 36
We would convert from radians to degree
1 pi rad = 180 degrees
pi/2 rad = 180/2 = 90 degrees
Thus, # = 90 degrees
The equation becomes
36 = 90/360 * 2 * pi * radius
36 = 0.25 * 2 * 3.14 * radius
36 = 1.57 * radius
radius = 36/1.57
radius = 22.93 feet