Extended wave solutions for a nonlinear Klein-Gordon-Zakharov system

The nonlinear Klein-Gordon-Zakharov (KGZ) system is used as a vehicle to employ the sine-cosine method and the extended tanh method to construct formally exact wave solutions. Each method presents various solutions with distinct formal properties and physical structures, which mainly include new periodic wave solutions, traveling wave solutions and solitary solutions. In addition, as special cases, some of new rational functions type solutions are developed and extended.