Who discovered/invented pi (π)?

Pi (π) wasn't "discovered" or "invented" by a single person at a specific moment. It's a mathematical constant representing the ratio of a circle's circumference to its diameter, and the understanding of this ratio evolved over thousands of years.

Ancient Awareness: Ancient civilizations knew that the ratio of a circle's circumference to its diameter was constant.

Babylonians (c. 1900-1600 BCE): Used approximations like 3 or 3.125.

Ancient Egyptians (c. 1650 BCE): The Rhind Papyrus suggests an approximation of about 3.1605.

Archimedes (c. 287-212 BCE): The Greek mathematician Archimedes was the first to rigorously estimate π using a method of inscribing and circumscribing polygons around a circle. He showed that π was between 3 10⁄71 (approx. 3.1408) and 3 1⁄7 (approx. 3.1429).

Symbol π: The Greek letter π was first used to denote this constant by Welsh mathematician William Jones in 1706. It was later popularized by Leonhard Euler in the 1730s.

Calculating More Digits: Over centuries, mathematicians developed more sophisticated methods (especially with the advent of calculus and infinite series) to calculate π to an increasing number of decimal places. Indian mathematicians like Madhava of Sangamagrama (c. 1400 CE) made significant progress using infinite series. With computers, π has now been calculated to trillions of digits.

Key Takeaway: The concept of pi was understood by ancient civilizations. Archimedes provided the first rigorous method for its calculation. The symbol π was introduced much later by William Jones and popularized by Euler. The pursuit of its precise value has continued throughout mathematical history.