% Compute and plot the green's function of eq. 2.8, section 2.1.1
clear;
x=0:0.05:1;
y=x;
I=length(x);
g=zeros(I,I);
for i=1:I
   for j=1:I
       if y(j) < x(i) 
	      g(i,j)=y(j)*(1-x(i));
	    else
		  g(i,j)=x(i)*(1-y(j));	   
	    end
	end
end

surf(x,y,g);
xlabel('x')
ylabel('y')