The length L of the chord joining the endpoints of an arc on a circle of radius r subtended by a central angle θ, 0 < θ ≤ π, is given by L =r√2 − 2 cosθ. Use this fact to approximate the field width (the width of scenery the lens can image) of a 450mm camera lens at a distance of 920 feet if the viewing angle of the lens is π/30.