contourplot(sin(x + cos(y)), x, 0, 3/2*%pi, y, 0, 3/2*%pi);
contourplot(tan(x*y), x, -%pi, %pi, y, -%pi, %pi);
contourplot(%e^(-sqrt(x^2 + y^2))*cos(atan(x/y)), x, -1, 1, y, -1, 1);
^