## Hipparchus

08 Nov

David Eugene Smith

Hipparchus (180 B.C – 125 B.C), the greatest of Greek astronomers, was born at Nicaea and died in Rhodes. His famous work on astronomy became the fundamental principle of science. As he needed to measure angles and distance on a sphere for his work, he developed a kind of spherical trigonometry. He made computation of chords of angles and in graphic solution of spherical triangles. In those computations, Hipparchus found some trigonometric formulas such as sin (AÂ±B), cos (AÂ±B), and the radius of the circumscribed circle (R=abc/4âˆ†). He also wrote about the theory of stereographic projection, a phase of geometry which has been proposed by Agatharchus (470 B.C). The theory was used by Hipparchus to represent the projection of the celestial sphere upon plane of the equator. He listed 850 fixed stars which increased to 1022 by Ptolemy (150 B.C) and there was no significant increase until modern time. Hipparchus also gave contribution in the making of Athenian Calendar.

Sri Rejeki, Herani Tri Lestiana

###

Together with my classmate, I made the summarize of Hipparchus from a book written by David Eugene Smith. It is one of the assignments in Historical Aspects of Classroom Mathematics course. This summarize then had to be compared with other students summarized of other sources and had to be analyzed individually. Yah, this is the very first assignment I do for this course and I will never forget the time when I get 2 or this assignment. 2 out of 4, it’s amazing 🙂

###

AN ANALYSIS OF HIPPARCHUS

About his lifetime, 4 sources mentioned 190BC – 120BC, 1 source mentioned that he was born in 190BC, 3 sources mentioned 180 – 125, 2 sources mentioned 175 – 125, 1 source mentioned he died in 125, 1 source mentioned that he was born 160 and a source only mentioned that it was second half BC. It is difficult to know the exact time, but perhaps the closest is around 190BC – 120BC because the other estimation is included in it. He is an astronomer, some books said ‘the greatest’ but some did not mention it. He used mathematics particularly trigonometry (planar and spherical trigonometry) in his work of astronomy. He is remembered especially because of his compilation of tables of chords (table of trigonometry). But, because every abstract only a brief description, some abstracts sometimes focus on different aspect. (Sri Rejeki)