Pi

A circle is a shape consisting of all points in a plane that are at a given distance from a given point, the centre. The distance between any point of the circle and the centre is called the radius. The length of a line segment connecting two points on the circle and passing through the centre is called the diameter. A circle bounds a region of the plane called a disc.

The radian, denoted by the symbol rad, is the unit of angle in the International System of Units (SI) and is the standard unit of angular measure used in many areas of mathematics. It is defined such that one radian is the angle subtended at the center of a plane circle by an arc that is equal in length to the radius. The unit is defined in the SI as the coherent unit for plane angle, as well as for phase angle. Angles without explicitly specified units are generally assumed to be measured in radians, especially in mathematical writing.

mathematical holiday on March 14

example of ancient Egyptian mathematics

1998 film directed by Darren Aronofsky

sequence of digits in the math constant π, incorrectly attributed to Feynman

theorem of number theory

spiral composed of right triangles, placed edge-to-edge

Infamous 1897 bill in the Indiana legislature that purported to set the value of π

mathematical proof

Texts belonging to the Śrauta ritual

theorem that every curve of constant width has perimeter π times its width

mathematical proof related to the constant pi

ratio of the circumference of a circle to its radius

history of calculating π to degrees of precision

Piphilology comprises the creation and use of mnemonic techniques to remember many digits of the mathematical constant pi|. The word is a play on the word "pi" itself and of the linguistic field of philology.

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thumb|right|Fractional approximations of

calculations of π through history

Vedic Sanskrit texts on religious matters and mathematics, attributed to Baudhayana

hebrew work on geometry