Function pi returns a close approximation of the irrational constant value of pi, also known as Archimedes' constant or Ludolph's constant. This value represents the ratio of a circle's circumference to its diameter. The pi function takes no parameter so the use of parentheses is not necessary. If parentheses are used, they must remain empty.
Because constant pi is an irrational value, it cannot be represented exactly using any finite number of digits. In order to reduce rounding errors, Calcute internally stores more fractional digits than it normally displays: