function [alpha,beta] = trilu(a,b,c)
%
%TRILU - Reduced LU decomposition of tridiagonal matrix.
%
n = length(a);  alpha = zeros(n,1);   beta = zeros(n,1);

alpha(1) = a(1);
for k = 2:n
    beta(k) = b(k)/alpha(k-1);
    alpha(k) = a(k)-beta(k)*c(k-1);
end
