If one of the diameters of the circle x2+y2−22x−62y+14=0 is a chord of the circle (x−22)2+(y−22)2=r2, then the value of r2 is equal to
Answer: 10
Solution
The first circle has center C(2,32) and radius r1=2+18−14=6. The second circle has center O(22,22). A diameter PQ of the first circle passes through C and is a chord of the second circle. The perpendicular from O to chord PQ passes through C (since PQ is a diameter of the first circle). In right triangle OCQ, where Q is an endpoint of the diameter on the first circle: ∣OC∣2+∣CQ∣2=∣OQ∣2. We have ∣OC∣2=(22−2)2+(22−32)2=2+2=4 and ∣CQ∣=r1=6. Thus r2=4+6=10.
JEE Main · 2022 · 28 Jun 2022 · Shift 2 · Integer answer