The intersection of the plane z 2 with the sphere x2 y2 z

The intersection of the plane z = -2 with the sphere x^2 + y^2 - z^2 = 9

x^2 + y^2 + z^2 = 9 ........equation 1

Given, plane z=2

Substitute z = 2 In equation 1

x^2 + y^2 + (2)^2 = 9

x^2 + y^2 + 4 = 9

x^2 + y^2 = 9 - 4

x^2 + y^2 = 5

x^2 +y^2 = r^2

Here, r = sqrt (5),

Centre (0,0)