Page 658 - Basic College Mathematics with Early Integers
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S E C T I O N 9.2 I PLANE FIGURES AND SOLIDS 635
A sphere consists of all points in space that are the same distance from a point
c.The point c is called the center of the sphere.The radius of a sphere is the distance
from the center to any point on the sphere.The diameter of a sphere is the distance
across the sphere passing through the center.
Diameter
Radius
Center
The radius and diameter of a sphere are related in the same way as the radius
and diameter of a circle.
d
#
d = 2 r or r =
2
Example 4 Find the radius of the sphere. PRACTICE 4
Find the diameter of the
Solution: The radius is half the diameter. sphere.
d
r = 36 ft
2 7 mi
36 feet
r = = 18 feet
2
The radius is 18 feet.
Work Practice 4
The cylinders we will study have bases that are in the shape of circles and
heights that are perpendicular to their base.
Height
Circular
base
The cones we will study have bases that are circles and heights that are perpen-
dicular to their base
Height
Circular
base
Answer
4. 14 mi
