“…Besides, the spectral methods have enormous rates of convergence, they also have high level of reliability. The spectral method were divided into four classifications: collocation [5,6,26,27], tau [8,20,24,41], Galerkin [14,15,23] and Petrov-Galerkin [4,29] method. The main idea of the spectral methods is to express the solution of the problem as a finite sum of given basis of functions (orthogonal polynomials or combination of orthogonal polynomials) and then to choose the coefficients in order to minimize the difference between the exact and the numerical solutions.…”