clc; clear; close all;
f = @(x,y) x.*cos(y)
fx = @(x,y) cos(y) 
fy = @(x,y) -x.*sin(y)

%f = c then x = c/cos(y)
% f(1,1) = ca 0.5
g = @(y) 0.5./cos(y)
g2 = @(y) 0.2./cos(y)
g3 = @(y) 0.8./cos(y)


h=0.1
[x,y]=meshgrid(0:h:2);
quiver(x,y,fx(x,y),fy(x,y))
axis equal
axis([0 2 0 2])
xlabel('x')
hold on
h=h/10;

%plot (g(0:h:2), 0:h:2)
%plot (g2(0:h:2), 0:h:2, 'r')
%plot (g3(0:h:2), 0:h:2, 'g')