[X1,X2] = meshgrid(-3.2:.01:3.2,-6.5:.01:6.5);
	plot([0 pi -pi],0,'ko','MarkerFaceColor', 'k'); hold on
	g = 9.81;
	F = X2.^2./2+g.*(1-cos(X1));
	[C,h] = contour(X1,X2,F,[0.1*g 0.5*g g 1.999*g]);
	colormap gray;	caxis([-5,1e5]);
					

	options = odeset('RelTol',1e-10);
	[X1,X2] = meshgrid(-3.142:.01:3.142,-6.5:.01:6.5);
	plot([0 pi -pi],0,'ko','MarkerFaceColor', 'k'); hold on
	g = 9.81;
	F = X2.^2./2+g.*(1-cos(X1))+X2.*sin(X1)./10;
	[C,h] = contour(X1,X2,F,[2*g],'LineWidth',2);
	colormap gray;caxis([-5,1000000]);
	[t,y] = ode45('pendelnlk_f',[0 20], [-4 6],options);
	pfeilportrait(y,'k',[0.03 0.15],0.4,0.2);