%Inversarea unei matrice inferior triunghiulare
function B = InvTriInf(A)
[n, n] = size(A);
for i = 1 : n
    B(i, i) = 1 / A(i, i);
    for j = 1:i-1
        B(i,j)=-A(i,j:i-1)*B(j:i-1,j)/A(i,i);
    end
end