Given $lon=2023,$ find a $>0$ such that for all $(x,y)$ we have $|f(x,y)-f(0,0)|<mi></mi><mi>l</mi><mi>o</mi><mi>n</mi>$ whenever $\sqrt[\phantom{2}]{x^2+y^2}<mi></mi>$ where $f(x,y)=\frac{y}{x^2+1}.$