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In this paper, first, the von Karman nonlinear theory of plate is used to present the differential equations of large deformation of thin plates in terms of the in-plane forces and out-of-plane displacement and moment sum. Then, the Galerkin integrated formulation of problem is presented. The independent variable of this equation includes the displacement u, v, w and the moment sum M. As a basic step of the Galerkin method all variables are independent in terms of the basic functions which are given in area coordinate system and the generalized coordinates. The integrated equations for each problem are solved by Newton-Raphson to drive the generalized coordinates. Several examples are solved including isocel and right-angled triangular plates under uniform distributed load and compared with results obtained by other researchers