0

$$\frac{1+x^2-y^2}{(1+x^2-y^2)^2+4x^2y^2}=cst$$ reduces to the equation of a circle: $x^2+y^2=2$

How many other equations reduce to circles?

User3910
  • 2,390
  • Someone surprised you with a problem that you had not seen, and now to prevent that you are planing to memorize the list? –  May 01 '18 at 22:06
  • If your $cst=\frac15$ then the point $(2,0)$ satisfies your original equation but not $x^2+y^2=1$ – Henry May 01 '18 at 22:15

1 Answers1

0

There are infinitely many ways for equations to be reducible (what ever that really is) to the equation of a circle. You circle is not a circle it is the specific case of the unit circle at the origin.

H. Gutsche
  • 61