Editing Central angle (section)

{{Short description|Measure of two radii meeting}}
[[Image:Sector central angle arc.svg|thumb|right|Angle AOB is a central angle]]

A '''central angle''' is an [[angle]] whose apex (vertex) is the center O of a circle and whose legs (sides) are [[radius|radii]] intersecting the circle in two distinct points A and B. Central angles are [[subtend]]ed by an [[Arc (geometry)|arc]] between those two points, and the [[arc length]] is the central angle of a circle of radius one (measured in [[radian]]s).<ref name=Oxford>{{cite web | url=http://web.cortland.edu/matresearch/OxfordDictionaryMathematics.pdf |title=Oxford Concise Dictionary of Mathematics, Central Angle| first1=C.|last1=Clapham|first2=J.|last2=Nicholson | publisher =Addison-Wesley | year =2009|page=122|accessdate=December 30, 2013}}</ref> The central angle is also known as the arc's [[angular distance]]. The arc length spanned by a central angle on a sphere is called ''[[spherical distance]]''.

The size of a central angle {{math|Θ}} is  {{math|0° &lt; Θ &lt; 360°}}  or   {{math|0 &lt; Θ &lt; 2π}} (radians). When defining or drawing a central angle, in addition to specifying the points {{mvar|A}} and {{mvar|B}}, one must specify whether the angle being defined is the convex angle (&lt;180°) or the reflex angle (&gt;180°). Equivalently, one must specify whether the movement from point {{mvar|A}} to point {{mvar|B}} is clockwise or counterclockwise.