Although Claudius Ptolemy is best remembered as an astronomer and geographer, he is also one of the influential astronomer/mathematician who pushed the geocentric theory.  His works include Almagest and the Geography.  In Almagest, Ptolemy shows the mathematical theory of the motions of the celestial bodies.  He also gives details on the motions of each of the planets known to
astronomers during his time.  Ptolemy's geometric models were based on Aristotle's Earth-centered system. It is important to note that Ptolemy also generated geometrical proofs.  He approximated the  root of 3 to equal a chord of 60 degrees.  Ptolemy is one of several mathematicians who has a crater named after himself.

Author: Filiberto Barajas

References:
1.  Biography in Dictionary of Scientific Biography (New York 1970-1990).
2.  Biography in Encyclopedia Britannica.

URL:http://www-groups.dcs.st-and.ac.uk/~history/Mathematics/Ptolemy.html