Two chords, AB and CD, are drawn in a circle with center O. The chords are at the same perpendicular distance from the center, with OP = OQ. Using properties of circles and Pythagoras' theorem, it is shown that OA = OC and AP = CQ. Since the perpendicular from the center bisects each chord, 1/2AB = 1/2CD, and therefore AB = CD. The conclusion is that two chords at the same perpendicular distance from the center are equal in length.