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A sphere is a body bounded by a surface whose every point is
equidistant (i.e. the same distance) from a fixed point, called the
centre. For example, a shot (a heavy iron ball) is a solid sphere and a
tennis ball is a hollow sphere.
One-half of a sphere is called a
hemisphere.
Archimedes discovered that a cylinder that circumscribes a sphere, as
shown in the following diagram, has a curved surface area equal to the
surface area, S, of the sphere.
Example 32
Solution:
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