Answer:
The equator the circle is;
x^2 + y^2 = 36
Explanation:
The general equation of a circle is ;
(x-a)^2 + (y-b)^2 = r^2
(a,b) is the center of the circle which is the origin here
The radius is half the distance from edge to edge, passing through the center either in the vertical or horizontal direction
From the center to the edge of the positive x axis bounding the circle, we have 6 units
This would be the same for the left too
So, the diameter of the circle would be 6 + 6 = 12 units
The radius of the circle is half of this which would be 12/2 = 6 units
thus, we have the equation of the circle as;
(x-0)^2 + (y-0)^2 = 6^2
x^2 + y^2 = 36