x=linspace(-5,5,4);y=1./(1+x.^2);
hold on
xx=linspace(-5,5);
yy=lagrange(x,y,xx);
plot(xx,yy,'b')
hold on
xx1=linspace(-5,5,8);yy1=1./(1+xx1.^2);
yy2=lagrange(xx1,yy1,xx);
plot(xx,yy2,'r')
hold on
xx3=linspace(-5,5);yy3=1./(1+xx3.^2);
plot(xx3,yy3,'y')
hold on