Hi!
Let's define
f[x_, y_] = 1/(x^2 + y^2);
and draw two contours:
ContourPlot[{f[x, y] == 3, f[x, y] == 11}, {x, -1, 1}, {y, -1, 1}]
The result is OK:
But if we draw the same contours in another way:
ContourPlot[f[x, y], {x, -1, 1}, {y, -1, 1}, Contours -> {3, 11}, ColorFunction -> (White &)]
the result is
Where is the inner circle?
WBR, Vladimir,
P. S. For the inverse function both contours are in their places:
ContourPlot[1/f[x, y], {x, -1, 1}, {y, -1, 1}, Contours -> {1/3, 1/11}, ColorFunction -> (White &)]
