Q.

The length of tangent drawn to a circle of radius 9 cm from a point 41 cm from the centre is:

1 40 cm  
2 9 cm  
3 41 cm  
4 50 cm  

Ans.

(1)

Let O be the centre of the circle and P be the external point and PA is tangent at A as shown in Fig.

 OA  PAGiven, OA = 9 cm and OP = 41 cmIn right ΔOAP, we haveOP2=OA2+PA2(Using Pythagoras theorem)(41)2=(9)2+(PA)21681-81=PA21600=PA2PA=40 cm