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π (greek letter pi) is the ratio of the circumference of a circle to its diameter. π is about 3.14159265358979. A full circle has 2*pi() radians.

In Free Pascal's RTL, system.pi is a function which returns the value of π. This allows you to assign addr(system.pi) to a procedural variable.

pi()/4 is the same as arctan(1).

See also