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The number π (/ p aɪ /; spelled out as "pi") is a mathematical constant that is the ratio of a circle's circumference to its diameter, approximately equal to 3.14159.The number π appears in many formulae across mathematics and physics.
The following list includes the continued fractions of some constants and is sorted by their representations. Continued fractions with more than 20 known terms have been truncated, with an ellipsis to show that they continue. Rational numbers have two continued fractions; the version in this list is the shorter one.
where C is the circumference of a circle, d is the diameter, and r is the radius.More generally, = where L and w are, respectively, the perimeter and the width of any curve of constant width.
Thus all three corresponding sides are in the same proportion; in particular, we have C′A : C′C = C′P : C′A and AP : C′A = CA : C′C. The center of the circle, O, bisects A′A, so we also have triangle OAP similar to A′AB, with OP half the length of A′B. In terms of side lengths, this gives us
S n is the approximation after taking n terms. Each subsequent subplot magnifies the shaded area horizontally by 10 times. (click for detail) He used the first 21 terms to compute an approximation of π correct to 11 decimal places as 3.141 592 653 59. He also improved the formula based on arctan(1) by including a correction:
The word is a play on the word "pi" itself and of the linguistic field of philology. There are many ways to memorize π , including the use of piems (a portmanteau , formed by combining pi and po em ), which are poems that represent π in a way such that the length of each word (in letters) represents a digit. [ 1 ]
Proofs of the mathematical result that the rational number 22 / 7 is greater than π (pi) date back to antiquity. One of these proofs, more recently developed but requiring only elementary techniques from calculus, has attracted attention in modern mathematics due to its mathematical elegance and its connections to the theory of Diophantine approximations.
Pi (/ˈpaɪ/; Ancient Greek /piː/ or /peî/, uppercase Π, lowercase π, cursive ϖ; Greek: πι) is the sixteenth letter of the Greek alphabet, meaning units united, and representing the voiceless bilabial plosive IPA:. In the system of Greek numerals it has a value of 80. It was derived from the Phoenician letter Pe ().