Who is considered the founder of trigonometry?

Hipparchus of Nicaea ( c. 190 – c. 120 B.C.) a Greek astronomer, geographer, and mathematician. He is considered the founder of trigonometry.

Hipparchus was born in Nicaea, Bithynia (now İznik, Turkey), and probably died on the island of Rhodes, Greece. He developed trigonometry and constructed trigonometric tables, and he solved several problems of spherical trigonometry.

Trigonometry (from Greek trigōnon, "triangle" and metron, "measure") is a branch of mathematics that studies relationships between side lengths and angles of triangles. The field emerged in the Hellenistic world. The Greeks focused on the calculation of chords.

Throughout history, trigonometry has been applied in areas such as geodesy, surveying, celestial mechanics, and navigation.