Calculs de Présentations de Groupes Fuchsiens via les Graphes Rubanés

We show how to compute a geometrical presentation for a finitely generated fuchsian group G from the explicit knowledge of a fundamental polygon for G. We use a previous work on fat-graphs [4]. In particular, our result is a complement to the works of R.S. Kulkarni [10] and S. Johansson [5] on arithmetic fuchsian groups.