%Chazhibijiao.m
x=-5:0.1:5;z=0*x;y=1./(1+x.^2);
plot(x,z,'k',x,y,'r')
axis([-5 5 -1.5 2]);
pause,
hold on
for n=2:2:10
   x0=linspace(-5,5,n+1);   y0=1./(1+x0.^2);
   x=-5:0.1:5; y1=lagrangen(x0,y0,x);
   plot(x,y1)
   , pause
end
y2=1./(1+x0.^2);y=interp1(x0,y2,x);
plot (x,y,'k'),hold off
gtext('n=2'),gtext('n=4'),gtext('n=6')
gtext('n=8'),gtext('n=10')
gtext('f(x)=1/(1+x^2)')