There are many formulas of π of many types. Among others, these include series, products, geometric constructions, limits, special values, and pi iterations. π is intimately related to the properties of circles and spheres. For a circle of radius r, the circumference and area are given by C | = | 2π r A | = | π r^2. Similarly, for a sphere of radius r, the surface area and volume enclosed are S | = | 4π r^2 V | = | 4/3 π r^3.

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