That is not an illustration of eight quadratic curves, it is an illustration of four. "The figure below shows how the curve x^2+y^2−1=0 is approximated by four

That is not an illustration of eight quadratic curves, it is an illustration of four. "The figure below shows how the curve x^2+y^2−1=0 is approximated by four quadratic curves (in red). An approximation by eight quadratic curves is just about indistinguishable from a true circle."