Who is the father of trigonometry?

The title "father of trigonometry" is most often attributed to the Greek astronomer and mathematician Hipparchus of Nicaea (c. 190 – c. 120 BCE).

Why Hipparchus?

First Trigonometric Table: He is credited with compiling the first known trigonometric table, which listed lengths of chords in a circle corresponding to different angles. A chord is a line segment whose endpoints both lie on a circle, and chord lengths are related to modern sine functions.

Systematic Use: Hipparchus systematically used his table and trigonometric methods to solve astronomical problems, such as predicting solar and lunar eclipses and determining the positions of stars and planets.

Foundational Work: His work laid the groundwork for the development of trigonometry as a distinct branch of mathematics.

Earlier Influences: While Hipparchus is central, earlier mathematicians and astronomers in Babylonian, Egyptian, and even earlier Greek cultures had worked with ratios of sides of triangles and practical geometric techniques that were precursors to trigonometry.

Later Developments: Trigonometry was further developed by later mathematicians, including Menelaus of Alexandria, Ptolemy (whose Almagest included extensive trigonometric tables and applications to astronomy), and Indian mathematicians like Aryabhata (who developed sine tables).

Hipparchus is generally considered the "father of trigonometry" because he was the first known individual to systematically develop and use trigonometric tables (chord tables) to solve problems, primarily in astronomy.