Solution:
Two concentric circles with center O
OP and OB are the radii of the circles respectively, then
OP = 5 cm, OB = 13 cm.
Ab is the chord of outer circle which touches the inner circle at P.
OP is the radius and APB is the tangent to the inner circle.
In the right angled triangle OPB, by Pythagoras axiom,
OB2 = OP2 + PB2
132 = 52 + PB2
169 = 25 + PB2
PB2 = 169 – 25
= 144
PB = 12 cm
But P is the mid-point of AB.
AB = 2PB
= 24 cm