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Sphere



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An image of a sphere

A sphere is a shape in space that is like the surface of a ball. Usually, the words ball and sphere mean the same thing. But in mathematics, a sphere is the surface of a ball, which is given by all the points in three dimensional space that are located at a fixed distance from the center. The distance from the center is called the radius of the sphere. When the sphere is filled in with all the points inside, it is called a ball.

Common things that have the shape of a sphere are basketballs, superballs, and playground balls. The Earth and the Sun are nearly spherical, meaning sphere-shaped.

A sphere is the three-dimensional analog of a circle.

Volume

The volume ([math]V[/math]) of a sphere is given by

[math]\!V = \frac{4 \pi r^3}{3}[/math]

where [math]r[/math] is the radius of the sphere.

Surface area

The surface area ([math]A[/math]) of a sphere is given by

[math]\!A =4 \pi r^2[/math]

where [math]r[/math] is the radius of the sphere.

Equation of a sphere

In Cartesian coordinates, the equation for a sphere with a center at ([math]x_0[/math], [math]y_0[/math], [math]z_0[/math]) is as follows:

[math](x-x_0)^2 + (y-y_0)^2 + (z-z_0)^2 = r^2[/math]

where [math]r[/math] is the radius of the sphere.