Archimedes' constant is also known by what other name?

The number pi (π) is a mathematical constant. It is defined as the ratio of a circle's circumference to its diameter, and it also has various equivalent definitions. It appears in many formulas in all areas of mathematics and physics. It is approximately equal to 3.14159. It has been represented by the Greek letter "π" since the mid-18th century, and is also spelled out as "pi". It is also called Archimedes' constant.

Being an irrational number, π cannot be expressed as a common fraction, and equivalently its decimal representation never ends and never settles into a permanently repeating pattern. The digit sequence of π is conjectured to satisfy a specific kind of statistical randomness, but to date, no proof of this has been discovered.

Ancient civilizations required fairly accurate computed values to approximate π for practical reasons, including the Egyptians and Babylonians. Around 250 BC the Greek mathematician Archimedes created an algorithm for calculating it. In the 5th century AD Chinese mathematics approximated π to seven digits.

In the 20th and 21st centuries, mathematicians and computer scientists discovered new approaches that, when combined with increasing computational power, extended the decimal representation of π to many trillions of digits after the decimal point. Practically all scientific applications require no more than a few hundred digits of π.