The circumference of the sircle is: C = 128 ft. The central angle of the arc AB is 45 degrees. Therefore it takes 1/8 of the circumference: AB = 1/8 * 128 = 16 ft. Also C = 2 r Pi and the length of an arc is : L = r Pi Alpha / 180 degrees. It means that L= C / 2 * 45 / 360 = 16 ft. Answer: The length of AB is 16 ft. Hope this helps. Let me know if you need additional help!