function  HW5_4(n)
 
 P = @(x) cos(1/x);
 P_A = @(x) P(x) - (P(x+1)-P(x))^2 / (P(x+2)-2*P(x+1)+P(x));
 S = 1;
 
 E = @(x) P(x) - S;
 E_A = @(x) P_A(x) - S;
 
 for i = 1:n
	fprintf('n = %3.0f %16.8f\n', i, E_A(i) / E(i+2));
end
 
 end
 
 %Result: n = 100       0.33995921