Equation of sphere, x2+y2+z2+2x−2y−4z−19=0 .......(ii) and equation of plane x+2y+2z+7=0 .......(ii) centre of the sphere (−1,1,2) and radius of the sphere R=√1+1+4+19 =√25=5 Now, p= perpendicular distance from the centre to the plane p=
|−1+2+4+7|
√1+4+4
=
12
√9
=
12
3
=4
In ΔAOC R2=p2+r2 ⇒ r2=R2−p2 ⇒ r2=25−16=9 ⇒r=3