A característica de Euler-Poincaré
We introduce the Euler-Poincaré's characteristic with an elementary way and historically. We explain also why one should call Descartes-Poincaré characteristic instead of the Euler-Poincaré's characteristic. All the considered spaces are compact and without boundary. We work essentially on smooth and oriented surfaces . However, we work also on singular and non-oriented surfaces. We provide also the results which may be extended for the case of superior dimension.
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