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P. 120
Circles
5. Compare the lengths you obtained. Chord
E
What is the name of the lengths Y Secant line
OA, OB, or
OA, OB, or OC and OC as related to the Segment H P
circle? Tangent line
D O
FOR ONLINE READING ONLY
G R
6. Draw a line from point A to O and X
extend it to touch the circular edge Arc
of the object. Label the point with F Sector
A B Q
letter D.
Figure 5.1: Parts of a circle
7. Measure the length AD and A tangent to a circle is a line which
compare it with the lengths OA , touches the circle at only one point R.
OB, and OC. From your previous In Figure 5.1, line PQ is a tangent. A
knowledge about circles, what is the chord is a line segment which joins any
name of length AD? two points on the circle. In Figure 5.1,
line segments DE and GH are chords
8. Put a piece of thread around the
of the circle. A secant is a line which
circular edge of the object (from
intersect a circle at two points, a line
point A around and back to point A),
XGHY is a secant of a circle.
then stretch the thread on a metre
rule to obtain the length. What An arc is any part of the circumference
do you call this length? Are there of a circle. The parts AB, FG, and DA
some other ways of finding the same are examples of arcs of the circle shown
length? Explain? in Figure 5.1. A segment is any part of
a circular region which is bounded by a
9. Draw a circle and indicate all the chord and an arc. In Figure 5.1, the red
parts of a circle you have identified part is a segment of a circle.
in this activity.
A sector is any part of a circular region
10. Share your results with the rest of which is bounded by two radii and an arc.
the class through discussion. In Figure 5.1, part AOBA is an example Mathematics for Secondary Schools
of a sector which is formed by two radii
AO and BO, and the arc AB.
In Activity 5.1, you have identified the
common parts of a circle. Other parts Exercise 5.1
of a circle include a segment, a chord, a
1. Write an equation that shows how
sector, an arc, secant line, and a tangent
the diameter of a circle is related to
line. These parts are summarized in
the radius of the circle.
Figure 5.1.
Student\s Book Form Three 113
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MATHEMATIC F3 SB.indd 113 18/09/2025 09:59:34
MATHEMATIC F3 SB.indd 113
