Kabouya, Nesrine2020-10-192020-10-192020https://repository.univ-msila.dz/handle/123456789/19985In this thesis we studied Bessel functions and series of solutions to a second order differential equation (bessel equation) And some characteristics of applications of Bessel functions in mathematical equations as well as in the physical fields whereas that arise in many diverse situations, Develops the different kinds of Bessel functions equation as applied to that the solution in each case which is present in the solution of Bessel differential equation are the same.enBessel differential equation, Bessel functions, Hankel functions, Neumann functions, Bessel-type functions, linear ordinary differential equations, Hilbert space, gamma functionThesis