Let C be a circle having centre in the first quadrant and touching the x-axis at a distance of 3 units from the origin. If the circle C has an intercept of length 6 3 on y-axis, then the length of the chord of the circle C on the line x-y=3 is :
- 8
- 6
- 6 2
- 8 2
Answer
(3) 6 2
Solution
[figure]
The circle touches the x-axis at (3, 0) and its centre is in the first quadrant
centre (3, r), radius r
Distance of the centre from the y-axis =3
intercept on y-axis =2 r2-9=6 3
r2-9=27 r=6
Centre (3, 6), radius 6
Distance of the centre from x-y-3=0: p= |3-6-3| 2=3 2
Length of chord =2 r2-p2=2 36-18=6 2
Answer: (3)