The circumference is the distance around a closed curve. Circumference is a kind of perimeter.
The circumference of a circle can be calculated from its diameter using the formula:
c = πd
Or, substituting the radius for the diameter:
c = 2πr
Where r is the radius and d is the diameter of the circle, and π (the Greek letter pi) is the constant 3.141 592 6...
The circumference of an ellipse is more problematical, the exact solution being an infinite series. A good approximation is Ramanujan's:
where a and b are the ellipse's semi-major and semi-minor axes, respectively. The two are related by the ellipse's eccentricity as follows:
Which means the circumference can also be written as:
- Numericana - Circumference of an ellipse http://home.att.net/~numericana/answer/ellipse.htm#elliptic
Last updated: 02-10-2005 01:52:47