102,863
edits
Changes
Created page with 'File:lighterstill.jpgright|frame ==Etymology== Latin, ray, radius *Date: circa [http://www.wikipedia.org/wiki/17th_Century 1611] ==Definitions==...'
[[File:lighterstill.jpg]][[File:Radius.jpg|right|frame]]
==Etymology==
[[Latin]], [[ray]], radius
*Date: circa [http://www.wikipedia.org/wiki/17th_Century 1611]
==Definitions==
*1 : a line segment extending from the [[center]] of a [[circle]] or [[sphere]] to the [[circumference]] or bounding [[surface]]
*2 a : the bone on the thumb side of the [[human]] forearm; also : a [[corresponding]] part of vertebrates above fishes
:b : the third and usually largest vein of an insect's wing
*3 a : the length of a radius <a truck with a short turning radius>
:b : the [[circular]] area defined by a stated radius
:c : a bounded or [[circumscribed]] area
*4 : a radial part
*5 : the distance from a [[center]] line or point to an [[axis]] of [[rotation]]
==Description==
In classical [[geometry]], a '''radius''' of a [[circle]] or [[sphere]] is any line segment from its [[center]] to its [[perimeter]]. By extension, the radius of a circle or sphere is the length of any such segment, which is half the [[diameter]].
More generally — in [[geometry]], science, engineering, and many other [[contexts]] — the radius of something (e.g., a cylinder, a polygon, a [[mechanical]] part, a hole, or a [[galaxy]]) usually refers to the distance from its [[center]] or [[axis]] of [[symmetry]] to a point in the [[periphery]]: usually the point farthest from the [[center]] or [[axis]] (the outermost or maximum radius), or, sometimes, the closest point (the short or minimum radius). If the object does not have an obvious [[center]], the term may refer to its circumradius, the radius of its [[circumscribed]] circle or circumscribed sphere. In either case, the radius may be more than half the [[diameter]] (which is usually defined as the maximum distance between any two points of the figure)
The inradius of a [[geometric]] figure is usually the radius of the largest [[circle]] or [[sphere]] contained in it. The inner radius of a ring, tube or other hollow object is the radius of its cavity.
The radius of a regular polygon (or polyhedron) is the distance from its [[center]] to any of its [[vertices]]; which is also its circumradius. The inradius of a regular polygon is also called [http://en.wikipedia.org/wiki/Apothem apothem].
In [http://en.wikipedia.org/wiki/Graph_theory graph theory], the radius of a graph is the minimum over all [[vertices]] u of the maximum distance from u to any other [[vertex]] of the graph.
The [[name]] comes from [[Latin]] radius, meaning "ray" but also the spoke of a chariot [[wheel]]. The plural in [[English]] is radii (as in [[Latin]]), but radiuses can be used, though it rarely is.[http://en.wikipedia.org/wiki/Radius]
[[Category: Mathematics]]
==Etymology==
[[Latin]], [[ray]], radius
*Date: circa [http://www.wikipedia.org/wiki/17th_Century 1611]
==Definitions==
*1 : a line segment extending from the [[center]] of a [[circle]] or [[sphere]] to the [[circumference]] or bounding [[surface]]
*2 a : the bone on the thumb side of the [[human]] forearm; also : a [[corresponding]] part of vertebrates above fishes
:b : the third and usually largest vein of an insect's wing
*3 a : the length of a radius <a truck with a short turning radius>
:b : the [[circular]] area defined by a stated radius
:c : a bounded or [[circumscribed]] area
*4 : a radial part
*5 : the distance from a [[center]] line or point to an [[axis]] of [[rotation]]
==Description==
In classical [[geometry]], a '''radius''' of a [[circle]] or [[sphere]] is any line segment from its [[center]] to its [[perimeter]]. By extension, the radius of a circle or sphere is the length of any such segment, which is half the [[diameter]].
More generally — in [[geometry]], science, engineering, and many other [[contexts]] — the radius of something (e.g., a cylinder, a polygon, a [[mechanical]] part, a hole, or a [[galaxy]]) usually refers to the distance from its [[center]] or [[axis]] of [[symmetry]] to a point in the [[periphery]]: usually the point farthest from the [[center]] or [[axis]] (the outermost or maximum radius), or, sometimes, the closest point (the short or minimum radius). If the object does not have an obvious [[center]], the term may refer to its circumradius, the radius of its [[circumscribed]] circle or circumscribed sphere. In either case, the radius may be more than half the [[diameter]] (which is usually defined as the maximum distance between any two points of the figure)
The inradius of a [[geometric]] figure is usually the radius of the largest [[circle]] or [[sphere]] contained in it. The inner radius of a ring, tube or other hollow object is the radius of its cavity.
The radius of a regular polygon (or polyhedron) is the distance from its [[center]] to any of its [[vertices]]; which is also its circumradius. The inradius of a regular polygon is also called [http://en.wikipedia.org/wiki/Apothem apothem].
In [http://en.wikipedia.org/wiki/Graph_theory graph theory], the radius of a graph is the minimum over all [[vertices]] u of the maximum distance from u to any other [[vertex]] of the graph.
The [[name]] comes from [[Latin]] radius, meaning "ray" but also the spoke of a chariot [[wheel]]. The plural in [[English]] is radii (as in [[Latin]]), but radiuses can be used, though it rarely is.[http://en.wikipedia.org/wiki/Radius]
[[Category: Mathematics]]