Transcript Section 1.1 - West Ada School District / Homepage

9-1
Exploring Circles
Objectives:
• To identify and use parts of circles.
• To solve problems involving the circumference of a
circle.
Vocabulary
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Circle
Center
Radius
Chords
Diameter
Circumference
π (pi)
Vocabulary
• A circle is the set of all
points in a plane that are
a given distance from a
given point in the plane.
• That point is the center of
the circle.
Vocabulary
• A radius of the circle is a
segment that one
endpoint at the center of
the circle and the other
endpoint on the circle.
• All radii are congruent to
each other.
Vocabulary
• A chord of a circle is a
segment that has its
endpoints on the circle.
• RF and KL are both
chords of Circle P.
• KL is also a diameter of
Circle P.
Circumference of Circle
• If a circle has a circumference of C units and a
radius of r units, then C = 2πr.
C  2r
C  d
Example 1
• Find the circumference of a circle with a radius
of 6.8 centimeters.
C  2r
C  d
Example 2
• Find the exact circumference of Circle P.