Transcript Circles

Lesson 8-1
Circle
Terminology
Lesson 8-1: Circle Terminology
1
Circle Definition
Circle : The set of points coplanar points equidistant from a
given point.
The given point is called the CENTER of the circle.
The distance from the center to the circle is called the RADIUS.
Center
Radius
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Definitions
Chord : The segment whose endpoints lie on the circle.
Diameter : A chord that contains the center of the circle.
Tangent : A line in the plane of the circle that intersects the circle
in exactly one point.
Point of Tangency :
The point where the tangent line intersects
the circle.
Secant : A line that contains a chord.
Diameter
Secant
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Example: In the following figure identify
the chords, radii, and diameters.
Chords:
B
C
AB, BF , CE
A
O
Radii:
D
F E
Diameter: FB
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Definitions
Congruent Circles :
Circles that have congruent radii.
2
2
Concentric circles : Circles that lie in the same plane and
have the same center.
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Polygons
Inscribed Polygon:
A polygon inside the circle whose vertices
lie on the circle.
Circumscribed Polygon :
A polygon whose sides are
tangent to a circle.
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ARCS
Arcs : The part or portion on the circle from some point B to C
B
is called an arc.
Example:
Semicircle:
C
BC
A
B
An arc that is equal to 180°.
A
Example:
ABC
O
C
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Minor Arc & Major Arc
Minor Arc : A minor arc is an arc that is less than 180°
A minor arc is named using its endpoints with an “arc” above.
A
Example:
AB
Major Arc:
A major arc is an arc that is
greater than 180°.
B
A
B
A major arc is named using its endpoints along
with another point on the arc (in order).
O
C
Example:
Lesson 8-1: Circle Terminology
ABC
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Example: ARCS
Identify a minor arc, a major arc, and a semicircle, given that
is a diameter.
Minor Arc:
CD
DE, EC, CF , DF
E
D
Major Arc: CEF , EDC, DFE, FCD
A
C
F
Semicircle: CED, CFD, EDF , ECF
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