Where did the symbol pi come from?

Answer 1

Pi is a letter in the Greek alphabet. Greek letters are used for many mathematical quantities, especially variables in formulas, such as theta for an angular measurement, and of course pi for the ratio of the diameter to the circumference of a circle. Pi notation was first used by the English mathematician William Jones in 1706. The pi notation was used by Euler as early as 1737. Thereafter, pi became the standard notation for this all-important ratio and transcendental constant.