A
two-dimensional perspective projection of a sphere
A sphere (from Greek σφαῖρα-sphaira, "globe,
ball") is a perfectly round geometrical object in three-dimensional space, such
as the shape of a round ball. Like a circle in two dimensions, a perfect sphere is completely symmetrical around its center, with all
points on the surface lying the same distance r from the center point. This
distance r is known as the radius of the sphere. The maximum
straight distance through the sphere is known as the diameter of the sphere. It passes
through the center and is thus twice the radius.
In 3 dimensions, the volume inside a sphere (that is, the volume
of a ball) is given by the
formula
where r is the radius of the sphere and π
is the constant pi. (Our solved example in mathguru.com uses this concept)
http://en.wikipedia.org/wiki/Sphere
The
above explanation is copied from Wikipedia, the free encyclopedia and is
remixed as allowed under the Creative Commons Attribution- ShareAlike 3.0 Unported
License.