In the fig. given below, O is the center of the circle. If PA = 12cm, PC = 15cm and CD = 7cm. Find length of AB.
We can use the secant -secant theorem
PD = PC - CD = 15 - 7 = 8
We have that
PB ( PB + PA) = PD ( PD + DC)
PB ( PB + BA) = 8 ( 8 + 7)
PB ( PA) = 8 ( 15)
PB (12) =120
PB = 120 / 12 = 10
So
AB = PA - PB = 12 - 10 = 2
