The profile of the cables on a suspension bridge may be modeled by a parabola. the central span of the bridge is 1280 m long and 160 m high. the parabola y = 0.00039^2 gives a good fit to the shape of the cables, ixi less than of equal to 635, and x and y are measured in feet. approximate the length of the cables that stretch between the tops of the two towers.