Applying a new algorithm to derive nonclassical symmetries

Abstract In this paper we extend the procedure described for Bilă and Niesen in [Bilă N, Niesen J. On a new procedure for finding nonclassical symmetries. J Symbol Comp 2004;38:1523–33], to obtain the determining equations of the nonclassical symmetries associated with a partial differential equation system, to a different case. We offer some examples of how our method works. By using this procedure we obtain a new nonclassical symmetry for the 2 + 1-dimensional shallow water wave equation.