Let the circle have center O, radius r = 13 cm, and chord AB at a distance d = 12 cm from the center. Draw a perpendicular from O to chord AB, meeting at point M. Then, OM = 12 cm and AM = MB = AB/2. Using the right triangle OAM, by Pythagoras theorem: \[OA^2 = OM^2 + AM^2\] \[13^2 = 12^2 + AM^2\] \[169 = 144 + AM^2\] \[AM^2 = 169 - 144 = 25\] \[AM = 5 cm\] Length of chord AB = 2 × AM = 2 × 5 = 10 cm.