《DSP using MATLAB》Problem 4.12

function [As, Ac, r, v0] = invCCPP(b0, b1, a1, a2)
	% Determine the signal parameters Ac, As, r, v0 in terms of
	%   the rational function parameters b0, b1, a1 and a2.
	% ----------------------------------------------------
	% function [As, Ac, r, v0] = invCCPP(b0, b1, a1, a2)
	% 
	%  b0, b1 = numerator coefficient 
	%  a1, a2 = denominator coefficient 
	%    
	%  x(n)=Ac*(r^n)*cos(pi*v0*n)*u(n) + As*(r^n)*sin(pi*v0*n)*u(n)
	%
Ac = b0;
 r = sqrt(a2);
v0 = acos(-a1/(2*r));
As = (b1-a1*b0/2) / (r*sin(v0*pi));