format long
y=0;
Y=[(0.6-cos(0.6)) (0.7-cos(0.7)) (0.8-cos(0.8)) (0.9-cos(0.9))];
fY=[0.6 0.7 0.8 0.9];

L=[1 1 1 1];

ans=0;

for i=0:3
  a=1;
  for r=0:3
    if (r~=i)
     
      a=a*(y-Y(r+1))/(Y(i+1)-Y(r+1)); 
     
     
    end
  end

  L(i+1)=a;
  
end
for i=0:3

  ans=ans+L(i+1)*fY(i+1);

end
disp(ans);