  We present here a simple and direct proof of the classic geometric version of
Hahn-Banach Theorem from its analitic version, in the real case. The reciprocal
implication, and the direct proofs of both versions, are already well kown, but
they are also summarized. For the complex case, in both versions the
Hahn-Banach Theorem is deduced from the real case, as it is well known.
