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Journal of Nutritional Disorders & Therapy
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Expansion of Waist Circumference in Medical Literature: Potential Clinical Application of a Body Shape IndexJournal of Homeopathy & Ayurvedic Medicine
incidenceofzeequnnafasshoabibronchialasthmainindividualsofdifferenttemperamentsCircumference
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mathematical constant π 

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Circumference (from Latin circumferentia, meaning "carrying around") is the linear distance around the edge of a closed curve or circular object.^{[1]} The circumference of a circle is of special importance in geometry and trigonometry. Informally "circumference" may also refer to the edge itself rather than to the length of the edge. Circumference is a special case of perimeter: the perimeter is the length around any closed figure, but conventionally "perimeter" is typically used in reference to a polygon while "circumference" typically refers to a continuously differentiable curve.
Contents
Circumference of a circle
The circumference of a circle is the distance around it. The term is used when measuring physical objects, as well as when considering abstract geometric forms.
Relationship with Pi
The circumference of a circle relates to one of the most important mathematical constants in all of mathematics. This constant, pi, is represented by the Greek letter π. The numerical value of π is 3.14159 26535 89793 ... (see OEIS A000796). Pi is defined as the ratio of a circle's circumference C to its diameter d:
 <math> \pi = \frac{C}{d}</math>
Or, equivalently, as the ratio of the circumference to twice the radius. The above formula can be rearranged to solve for the circumference:
 <math>{C}=\pi\cdot{d}=2\pi\cdot{r}.\!</math>
The use of the mathematical constant π is ubiquitous in mathematics, engineering, and science. While the constant ratio of circumference to radius <math>{C}/{r} = 2\pi</math> also has many uses in mathematics, engineering, and science, it is not formally named. These uses include but are not limited to radians, computer programming, and physical constants.
Circumference of an ellipse
The circumference of an ellipse can be expressed in terms of the complete elliptic integral of the second kind.
Circumference of a graph
In graph theory the circumference of a graph refers to the longest cycle contained in that graph.
See also
References
 ^ San Diego State University (2004). "Perimeter, Area and Circumference" (PDF). AddisonWesley.
External links
40x40px  The Wikibook Geometry has a page on the topic of: Arcs 
40x40px  Look up circumference in Wiktionary, the free dictionary. 
 Numericana  Circumference of an ellipse
 Circumference of a circle With interactive applet and animation