Circle And System Of Circles Question 290
Question: An infinite number of tangents can be drawn from (1, 2) to the circle $ x^{2}+y^{2}-2x-4y+\lambda =0 $ , then $ \lambda = $
[MP PET 1989]
Options:
A) - 20
B) 0
C) 5
D) Cannot be determined
Show Answer
Answer:
Correct Answer: C
Solution:
Clearly the point (1, 2) is the centre of the given circle and infinite tangents can only be drawn on a point circle.
Hence radius should be 0.
$ \therefore ,\sqrt{1^{2}+2^{2}-\lambda }=0\Rightarrow \lambda =5 $ .
BETA
