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Sphere

A sphere is the set of all points in space at a given distance from a given point. The given distance is called the radius and the given point is the center.

Math diagram

Half of a sphere is called a hemisphere .

Math diagram

The surface area of a sphere is $4 π$ times the square of the radius. $(S . A . = 4 π r^{2})$

Example 1:

Find the surface area of a sphere with a radius of $11$ cm.
$S . A . = 4 π {(11)}^{2} = 484 π {cm}^{2}$ .

The volume of a sphere is four-thirds pi times the cube of the radius. $(V = \frac{4}{3} π r^{3})$

Example 2:

Find the volume of a sphere with a radius $2$ cm.

$\begin{array}{l} V = \frac{4}{3} π {(2)}^{3} = \frac{32 π}{3} {cm}^{3} \\ \approx 33.51 {cm}^{3} \end{array}$