perterm(T,C5,S5,C,S,IX,I,IT,DLC,DLS,DRC,DRS,DBC,DBS)

function [ddl,ddb,ddr] = perterm(T,C5,S5,C,S,IX,I,IT,DLC,DLS,DRC,DRS,DBC,DBS)

% function [ddl,ddb,ddr] = perterm(T,C5,S5,C,S,IX,I,IT,DLC,DLS,DRC,DRS,DBC,DBS)
%
% compute terms of perturbation
% algorithms by Montenbruck/Pfleger: "Astronomy with the Personal Computer"
%
% 05.05.04 M.Penzkofer

IX = IX+20;
I  = I+20;
U = 0;
V = 0;

if (IT == 0)
   [U,V] = addtheo(C5(IX),S5(IX),C(I),S(I));
else
   U = U*T;
   V = V*T;
end

ddl = DLC*U+DLS*V;
ddb = DBC*U+DBS*V;
ddr = DRC*U+DRS*V;