=1 Here, a2=16 and b2=9 We know that, foci of ellipse of
x2
a2
+
y2
b2
=1 is (±ae,0) =√16−9 =√7 ∴ Foci of ellipse (±√7,0) It is given that, centre of circle is (0, 3) and passes through ±√7,0∴r=√(0+√7)2+(3−0)2 √7+9 =4 Hence, radius of circle = 4 units