function p2
  
   format long
   a=[0.6 0.7 0.8 0.9];
   b=[cos(0.6) cos(0.7) cos(0.8) cos(0.9)];
   y=b-a;
   n= 3;
   Q=zeros(n+1);
   Q(:,1)=a';
   for i=1:n
      for j=1:i
         Q(i+1,j+1)=((0-y(i-j+1))*Q(i+1,j)-(0-y(i+1))*Q(i,j))/(y(i+1)-y(i-j+1));
      end
   end
   result=Q(n+1,n+1)
   ERR=result-cos(result)