Question

Derive equation of circle center at origin

Answer 1

An equation of the circle with center (h,k) and radius r is
(x-h)^2 + (y-k)^2 = r^2.

So, if the center is (0,0) and the radius is r, an equation of the circle is: (x-0)^2 + (y-0)^2 = r^2.

Simplifying, we get: x^2 + y^2 = r^2