% for question 2
format long;
xi=[0.6-cos(0.6) 0.7-cos(0.7) 0.8-cos(0.8) 0.9-cos(0.9)]';
fx=[0.6 0.7 0.8 0.9]';
A=zeros(4);A(:,1)=fx;
for i = 2:4
  for j = i:4
    A(j,i)=((0-xi(j-i+1))*A(j,i-1)-(0-xi(j))*A(j-1,i-1))/(xi(j)-xi(j-i+1));
    endfor
    endfor
A(4,4)