Before we do anything we must convert radians to degrees using a table. pi/3 radians equals 60 degrees, meaning the central angle of this arc is 60 degrees. This also tells us that the length of the arc is 1/6 of the whole circumference. All we have to do now is calculate the circumference which is diameter x pi.
arc = 1/6 pi x 36
arc = 6pi cm
