Circles

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Circles

by krishna kumar » Fri Jun 11, 2010 11:10 pm
In the xy-plane, the point (-2, -3) is the center of a circle. The point (-2, 1) lies inside the circle and the point (4, -3) lies outside the circle. If the radius r of the circle is an integer, then r =

A. 6
B. 5
C. 4
D. 3
E. 2

The OA given is B.

I haven't a clue to this. Could anyone help.

Thanks

krishna

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by kstv » Sat Jun 12, 2010 12:24 am
Centre is O (-2,-3) . Pt A (-2,1) is inside the circle. Dist OA is 4 - y coordianates ( -3 to 1) x coordiantes are same. The radius is > 4
Pt B (4,-3) so OB is 6 ( -2 to 4) , here y coordinate is - 3.
The radius is < 6.
The radius is an integer.
Left with no options other than B.

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by krishna kumar » Sat Jun 12, 2010 1:47 am
Thanks
:)