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.
Half of a sphere is called a hemisphere.
The surface area of a sphere is 4π times the square of the radius. (S. A. = 4πr2)
Example 1:
Find the surface area of a sphere with a radius of 11 cm.
S. A. = 4π (11)2 = 484π cm2.
The volume of a sphere is four-thirds pi times the cube of the radius. 
Example 2:
Find the volume of a sphere with a radius 2 cm.
≈ 33.51 cm3
