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What is Pi?

Pi is a number, approximately equal to 3.14159 (or 22/7) that expresses the ratio of the circumference to the diameter of a circle and appears as a constant in many mathematical expressions. Since Pi is one of the most important mathmatical and physical constants, Pi is an essential part of many mathmatic, science, and engineering formulas. Pi is also an irrational number which means that it is a real number that can not be expressed as a rational number. Pi is usually considered a transcendental number becuase it is a real number that is not an algebraic number. The Egyptians and Babylonians are credited with discovering Pi sometime around 4000 years ago. An English mathmematician, William Jones, selected the Greek letter to represent the ratio of a circle's circumference to its diameter in 1706.