Question 384082
XY is the equation for an hyperbola 
 
It's known that one can pass from hyperbolic to euclidean geometry via usage of complex number : 
 
let 

X=a+ib
Y=a-ib
 
then XY=a^2-aib+aib+b^2=a^2+b^2=10, hence it's a circle in the complex plane with radius sqrt(10)Ft.