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pi: the circle constant

pi represents π, the ratio of a circle’s circumference to its diameter. It is an exact mathematical constant used in geometry, trigonometry, probability, and complex analysis.

Common formulas

A circle of radius r has circumference 2 × pi × r and area pi × r². Angles in radians use π naturally: a half-turn is pi and a quarter-turn is pi/2.

Related functions

Use pi with sin(), cos(), and tan(). Convert angle units with asin() and acos(). Use numeric() only when a decimal approximation is required.

Precision

Keep pi symbolic for exact transformations; round a decimal only at the output boundary.

Try Pi in Calcul.io

Start with one of the editable examples above, then replace its arguments with your own values. Keeping the function on a separate calculator line makes the input and result easy to compare. For a longer workflow, assign the result to a variable or reference that line in the next expression.

Check the shown signature before adding optional arguments, and use the related-function links to compare operations with similar purposes.

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