1.6 Circles
___________ – The set of all points in a plane a given distance (the radius) from a given point (the
center).
circle
radius
center
____________ – A line segment from the center of a circle to a point on the circle, or the length of
this line segment.
____________ – The point from which all points on the circle are the same distance.
____________ – A line segment whose endpoints lie on a circle.
chord
__________________– A chord of a circle that contains the center.
diameter
__________________________ – Two circles that have the same radius length.
Geometry Lesson 1.6: Circles
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_____________________________ – Two or more circles having the same center.
_____________________ – A line that lies in the plane of a circle and that intersects the circle at
exactly one point.
point of tangency
tangent line
___________________________ – The point where a tangent line intersects the circle.
________________ – A line that intersects a circle in two points. It contains a chord of the circle.
secant
Geometry Lesson 1.6: Circles
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________ – Two points on the circle (the endpoints of the _______) and the points of the circle
between them. An angle intercepts an _______ if the sides of the angle intercept the circle at the
endpoints of the __________. The _________ is included by the chord with the same endpoints.
______________________ – An arc whose measure is less than the measure of a semicircle (180).
A minor arc is named with 2 points, the endpoints.
______________________ – An arc whose measure is greater than the measure of a semicircle
(180). A major arc is named using 3 points, the endpoint and any point on the arc between the
endpoints.
___________________________ - An arc of a circle included by a diameter. Half of a circle (180).
A semicircle is named using 3 points, the endpoints and any point on the semicircle between the
endpoints.
________________________ – An angle whose vertex is the center of a circle and whose sides pass
through the endpoints of a chord or arc.
minor arc
major arc
central angle
_____________________ – The measure of the central angle that intercepts an arc, measured in
degrees.
Geometry Lesson 1.6: Circles
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Example 1:
D
F
G
B
C
A
E
H
I
a) Name 2 chords.
b) Name 2 radii.
c) Name a diameter.
d) Name a tangent.
e) Name a secant.
Geometry Lesson 1.6: Circles
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Example 2:
BC is a diameter
m BAE = 46
m DAC = 73
D
C
B
A
E
a) Name a central angle.
b) Name a minor arc and find its measure.
c) Name a major arc and find its measure.
d) Name a semicircle.
pp. 70 – 71 => 1 – 10; 18 - 20
Geometry Lesson 1.6: Circles
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