2. What is a Circle?
A circle is a round plane figure whose
boundary (the circumference) consists of
points equidistant from a fixed point (the
center)
A circle is named by its center.
Ex. ʘ A
3. Which of the following are good
physical models of a circle?
5. Lessons and
Coverage
Lesson 1A – Chords, Arcs, and Central
Angles
Lesson
Lesson 1B – Arcs and Inscribed Angles
Lesson
Lesson 2A – Tangents and Secants of a
Circle
Lesson
Lesson 2B – Tangents and Secants
Segments
Lesson
6. Lesson 1A Chords, Arcs, and Central
Angles
OBJECTIVES
a.Identify the chords, arcs, central angles
and inscribed angles of a circle.
b.Name the chords, arcs, central angles,
and inscribed angles of a circle.
7. Activity 1
Use the figure below to identify and
name the following terms related to
ʘ O:
1. a radius
2. a diameter
3. A chord
4. A semicircle
5. a minor arc
6. a major arc
7. 2 central angles
8. 2 inscribed angle
8. Terms related to circle
Radius - is a straight line from
the center to the circumference
of a circle.
9. Terms related to circle
Diameter – a segment whose
endpoints lie on the circle and
whose midpoint is in the
center of the circle
10. Terms related to circle
Chord – is a line segment
joining two points on the
circumference of a circle.
11. Terms related to circle
Semicircle – an arc
measuring one-half the
circumference of a circle.
12. Terms related to circle
Minor arc – an arc of a circle
whose measure is less than
that of a semicircle
13. Terms related to circle
Major Arc – an arc of a
circle whose measure is
greater than that of a
semicircle
14. Terms related to circle
Central angle – an angle
formed by two rays/
segments whose vertex is
the center of a circle
15. Terms related to circle
Inscribed angle – an angle
whose vertex is on a circle
and whose sides contain
chords of the circle
16. Use ʘP below to identify and name
the following:
1. 2 radii
2. A diameter
3. 2 chords
4. 2 semicircles
5. 2 minor arcs
6. 2 major arcs
7. 2 central angles
8. 2 inscribed angles
17. Use ʘ O below to identify and
name the following:
1.radius
2.diameter
3.chord
4.semicircle
5.minor arcs
6.major arcs
7.central angles
8.inscribed angles
