[en] In this paper, we establish exact solutions for nonlinear equations. The sine-cosine method is used to construct periodic and soliton solutions of nonlinear physical models. Many new families of exact travelling wave solutions of the symmetric regularized long-wave (SRLW) and the Klein-Gordon-Zakharov (KGZ) equations are successfully obtained. These solutions may be important for the explanation of some practical physical problems. It is shown that the sine-cosine method provides a powerful mathematical tool for solving a great many nonlinear partial differential equations in mathematical physics