DICTIONARY‎ > ‎Geometry‎ > ‎

Circle

Description: 

A circle is a simple shape of Euclidean geometry that is the set of all points in the plane that are equidistant from a given point, the centre. The distance between any of the points and the centre is called the radius.




Area = pi x r²
C = pi x d          where pi=3.1415...


Center - point inside the circle. All points on the circle are equidistant in the same distance  from the center point.
Radius - the distance from the center to any point on the circle. It is half the diameter.
Chord - a line segment linking any two points on a circle.
Diameter - the distance across the circle. It is twice the radius. 
Circumference - the circumference is the distance around the circle.
Area - the region enclosed by the circle.


Two circles

disjoint




tangent



intersecting
outside                  inside



overlapping 
 Two circles which measures overlap to are called concentric    


Author(s):
Mikołaj Dobrzyński

Sources:
-http://en.wikipedia.org/wiki/Circle
-http://www.mathopenref.com/circle.html
-notebook for math :-)