[T,X] = meshgrid(-2:.01:2,-2:.01:2);
	F = T.*X.^2;
	[C,h] = contour(T,X,F,[0.1 0.5 1 2 3 4 5 -0.1 -0.5 -1 -2 -3 -4 -5]);
					

	[X1,X2] = meshgrid(-7:.01:7,-10:.05:10);
	F = 1./2 .* X2.^2-9.81.*cos(X1);
	[C,h] = contour(X1,X2,F,[0.0 0.5 1 2 3 4 -0.5 -0.85 -0.9999].*9.81);