% 
% Written by:
% -- 
% John L. Weatherwax                2009-04-21
% 
% email: wax@alum.mit.edu
% 
% Please send comments and especially bug reports to the
% above email address.
% 
%-----

close all; drawnow; clear functions; 
rehash; 
clc; 

format rat;

phi_1 = 1.2; 
phi_2 = -0.8; 

phi_11 = phi_1 / ( 1 - phi_2 ) 
num    = phi_1^2 / ( 1 - phi_2 ) + phi_2 - phi_1^2 / ( 1 - phi_2 )^2;  
den    = 1 - phi_1^2 / ( 1 - phi_2 )^2;  
phi_22 = num / den