Interesting observation It's because an inequation f(x,y)=g(x,y) only renders the boundary. A boundary exists when/where there's a sign flip or when there's a change from the function being defined to undefined. Desmos expects the result of an inequation to be in the form of a line/curve and not a region that's to be shaded (which is true in most cases so it works pretty well). So that is why it sometimes messes it up when the actual output of f(x,y)=g(x,y) should be a region and not just a line/curve because desmos only renders the boundary instead. For such cases, to truly show the entire region (and not just the boundary) when f=g, there's a workaround: 0<{f(x,y)=g(x,y)} https://www.desmos.com/calculator/l63udqxalx I came across such things multiple times and was very confused by it. Have added an extra example in the graph of when it happened to me. I hope that explains it. Answer from MathEnthusiast314 on reddit.com