In geometry, an arc is a closed segment of a differentiable curve in the two-dimensional plane; for example, a circular arc is a segment of the circumference of a circle. If the arc segment occupies a great circle (or great ellipse), it is considered a great-arc segment.
The length of an arc of a circle with radius r and subtending an angle 
(measured in radians) with the circle center — i.e., the central angle — equals 
. This is because
Substituting in the circumference
and solving for arc length, L, in terms of yields
An angle of α degrees has a size in radians given by
and so the arc length equals
[edit] See also
[edit] External links
- Definition and properties of a circular arc With interactive animation
- A collection of pages defining arcs and their properties, with animated applets Arcs, arc central angle, arc peripheral angle, central angle theorem and others.
- Eric W. Weisstein, Arc at MathWorld.
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