What is the history of pi in maths?

Answer 1

Historically, Ancient Egyptians are the first who introduced a reasonably accurate value for the ratio of the circle area and its square radius. They used an approximate value of 3.1605 for pi

The ancient Babylonians generally calculated the area of a circle by taking 3 times the square of its radius (=3), but one Old Babylonian tablet (from ca. 1900-1680 BD) indicates a value of 3.125 for pi.

The first theoretical calculation of a value of pi was that of Archimedes of Syracuse (287-212 BD), one of the most brilliant mathematicians of the ancient world. Archimedes worked out that 223/71 < pi < 22/7

The Greek letter π (pi) was adopted for the number from the Greek word for perimeter "περίμετρος", first by William Jones in 1707, and later popularized by Leonhard Euler in 1737. The constant is occasionally also referred to as the circular constant or Archimedes' constant.