clf
set(0,'defaulttextinterpreter','latex')
 
F1=@(x,y) x.*(1-y); F2=@(x,y) (1+x).*y;
x=linspace(-2,2,20);y=linspace(-2,2,21);
[X,Y]=meshgrid(x,y);
quiver(X,Y,F1(X,Y),F2(X,Y),1.5,'LineWidth',1.2)
hold on
axis([-2.5,2.5,-2.5,2.5])
axis equal
%set(gca,'YTickLabel',{})
% set(gca,'XTickLabel',{}) 
% set(gca,'ZTickLabel',{})
 text(-.5,2.2,'$\mathbf{F}(x,y) = x(1-y) \mathbf{i}+(1+x)y\mathbf{j}$','FontSize',14)

pause
 [X,Y]=meshgrid(-2:0.13:2,-2:.1:2);
 falt=@(x,y) y.*exp(-x-y)./x;
Z=falt(X,Y);
t=linspace(0,2*pi,14);
contour(X,Y,Z,[falt(cos(t),sin(t))],'k')
 te=text(-.5,-2.3,'F\"altlinjer: $\frac{y}{x}e^{-x-y} =C$','FontSize',14);
