1.

A straight line moves such that the algebraic sum of the perpendicularsdrawn to it from two fixed points is equal to `2k`. Then, then straight line always touches a fixed circle of radius.`2k`(b) `k/2`(c) `k`(d) none of theseA. 2kB. k/2C. kD. none of these

Answer» Correct Answer - C
Let the fixed points be `A(a, 0) and B(-a, 0)` and let the straight line be` y=mx+c`. Then,
`(mx+c)/(sqrt(1+m^(2)))+(-mx+c)/(sqrt(1+m^(2)))=2k " " ` [Given]
`rArr c=ksqrt(1+m^(2))`
Thus, the straight line is `y=mx+ksqrt(1+m^(2))`. Clearly, it touches the circle `x^(2)+y^(2)=k^(2)` whose radius is k.


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