Question

there are two concentric circles with centre O and of radii 5cm and 3cm. From an external point P, tangents PA and PB are drawn to these circles. If AP = 12cm, find the length of BP.

Answer 1

Answer:6cm

Step-by-step explanation:

Answer 2

Join OA and OB

Triangle OAP and OBP are right angled triangle.

In Triangle OAP 
AP= 12 cm , OA= 5 cm
OP2 = OA2 + AP2

          = 52 + 122
          =25 + 144 = 169

OP = 13 cm

 In Triangle OBP
 OP = 13 cm,  OB= 3 cm.

OP2 = OB2 +  BP2
OP2- OB2 = BP2
     =132 - 32 

     =169 -9
     = 160

BP = 4 root 10