cvgmt

@AlexTrounev Good job!

I think ContoutPlot rewrite f==g as f-g==0 and do with the function f-g

ContourPlot only support the two forms,that is "must be a function f or an equality of the form f == g", it means that f==g is not a boolean expression.

For example, ContourPlot[x^2 + y^2 == 1/2 == x^2 + y^2, {x, 0, 1}, {y, 0, 1}] can not work, so ContourPlot can not accept Boolean expression. The error messages as below : "must be a function f or an equality of the form f == g"

Maybe x^2 + y^2 == 1 || x^2 + y^2 == 2 is not a function about x and y.