Lagrange series and the Bessel function are two classical methods that were created by series expanding from Taylor series. In this paper, the purpose of those two methods was to find the values of the eccentric anomaly for one period (0–360)°. The Matlab program is used to apply the results, the input parameters were eccentricity (0–1), mean anomaly (0–360)°, and finally the parameter W (1–13). The program does not need a tolerance to obtain a precise value for eccentric anomaly like other iterative and non-iterative methods to stop the program; it will stop after completing the required period from 0° to 360° for a body that is determined by the solver. The output will be the final value of the eccentric anomaly. Furthermore, a compression between the Lagrange series and the Bessel function was studied to determine the eccentricity required for each method. The results showed that there was an increase in the relationship between the eccentric anomaly and the mean anomaly. Also, these two methods were used at eccentricity smaller or equal to 0.35 and for all ranges of W (1–13). More values for W in the Lagrange series produced a very large shift from the ideal solution. All of those results were in good agreement as compared with other published studies in this field.
