From Pythagoras theorem |OA|2 = |AN|2 + |ON|2 72 = |AN|2 + (5)2 49 = |AN|2 + 25 |AN|2 = 49 - 25 = 24 |AN| = \(\sqrt {24}\) = \(\sqrt {4 \times 6}\) = 2\sqrt6 cm |AN| = |NB| (A line drawn from the centre of a circle to a chord, divides the chord into two equal parts) |AN| + |NB| = |AB| 2\sqrt6 + 2\sqrt6 = |AB| |AB| = 4\sqrt6 cm