clear 
format long

x = [0.6 0.7 0.8 0.9];
e = [cos(0.6) cos(0.7) cos(0.8) cos(0.9)];

y = e - x;

n = size(x)(2);

Q = zeros(n);
Q(:,1) = x';
z = 0;

for i = 1:n-1
  for j = 1:i
    Q(i+1,j+1) = ( ((z-y(i-j+1))*Q(i+1,j)) - ((z-y(i+1))*Q(i,j)) ) / ( y(i+1) - y(i+1-j) );
  end  
end    


f = @(x) cos(x) - x
f(Q(n,n))
Q(n,n)