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# What is pi?

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Pi is the ratio of a circle's circumference to its diameter. The number pi, symbolized by a Greek letter, has a constant value that approximately equals 3.14. The distance around any circle when divided by its diameter always gives this exact result.

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This constant is commonly used to solve the area of a circle, with the formula "pi r^2“ or the product of pi and the square of the length of the radius. Pi is an irrational number, which means it cannot be expressed as a common fraction, and it has an infinite decimal representation without any repeating pattern. The rounded version of pi is accepted for general computations. Pi up to 20 decimal digits is 3.14159265358979323846.

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## Related Questions

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Pi is important in math because it describes how the circumference of a circle is in proportion to the diameter of a circle. To get pi, a mathematician divides the circumference of the circle by the diameter.

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Pi does not have units because it is a number, not a measurement. However, pi is sometimes treated like a unit when referring to angle measurements because the actual unit, radians, is a length divided by length and is therefore dimensionless.

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If the circumference or the area of a circle is known, pi can be used to find the diameter and the radius of that circle. Likewise, if the radius or diameter is known, pi can be used to find out the circumference or the area.

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Pi is an irrational number, so named because it cannot be expressed as the ratio of two integers. The decimal representation of an irrational number never ends or falls into a permanently repeating pattern.

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