function Mar29()
% Secant method error applied to f(x) = x^2 - A
%
% x(k+1) = x(k) - f(x(k))/ ( (f(x(k)) - f(x(k-1))/(x(k)-x(k-1)) )
%        = x(k) - (x(k)^2 - A)/ ((x(k)^2 - x(k-1)^2)/(x(k)-x(k-1)) )
%        = x(k) - (x(k)^2 - A)/(x(k)+x(k-1))
%
% Now subtract sqrt(A) from both sides and "play"