Diameter
November 20, 2009 at 12:40 am | Posted in Parts of a circle | Leave a commentThe diameter of a circle is the length of the line through the center and touching two points on its edge. In the figure above, drag the orange dots around and see that the diameter never changes.
Sometimes the word ‘diameter’ is used to refer to the line itself. In that sense you may see “draw a diameter of the circle”. In the more recent sense, it is the length of the line, and so is referred to as “the diameter of the circle is 3.4 centimeters”
The diameter is also a chord. A chord is a line that joins any two points on a circle. A diameter is a chord that runs through the center point of the circle. It the longest possible chord of any circle.
Radius
November 20, 2009 at 12:36 am | Posted in Parts of a circle | Leave a commentRadius of a Circle
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.[1]
More generally — in geometry, science,engeeniring, 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 shortminimum radius). If the object does not have an obvious center, the term may refer to its circumradius, the radius of its circumscribed circle or 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.[3]apothegm.
In 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.[4]
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.[5]
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