Furthermore, according to Poisson's Theorem, if two quantities A and B are explicitly time independent ( A ( p , q ) , B ( p , q ) ) constants of motion, so is their Poisson bracket { A , B } . This does not always supply a useful result, however, since the number of possible constants of motion is limited ( 2 n − − 1 for a system with n degrees of freedom), and so the result may be trivial (a constant, or a function of A and B .)