Page 119 - Mathematics_Form_3

Circles

Chapter Five

Circles
FOR ONLINE READING ONLY

Introduction

In the surrounding environment, there are various objects with circular shapes.
Round plates, buckets, bottles, round tables, circular house decorations, and
structures of many other objects are constructed based on the knowledge of
circles. In this chapter, you will learn the concept of a circle, central angles,
the arc length of a circle, the concept of radian measure, and circle theorems
of inscribed angles and chords. The competencies developed in this chapter
will be useful in various real life situations such as in building constructions,
manufacturing of goods, decorations, road designs, study of the universe,
and many other applications.

Think
Wheels, roundabouts, tunnels, clocks, orbits, water pipes, lenses
without the concept of circles.

Concept of a circle 2. Take one object and locate its centre
A circle is a closed curve whose every
using a piece of chalk or a marker
Mathematics for Secondary Schools fixed point, called the centre. Engage 3. Use a piece of chalk or a marker pen
point is at an equal distance from a
pen. Label the point with the letter
O.
in Activity 5.1 to identify and explore
different parts of a circle
to mark three points on the circular
edge of the object. Label the points
Activity 5.1: Identifying parts
with letters A, B, and C.
of a circle

Individually or in a group, perform the
following tasks:
ruler to measure the length from
1. Collect circular objects such as lids 4. Use a piece of thread and a metre
the centre O to the points A, B, and
of plastic buckets, circular coins
C on the circular edge. Record the
and bottles, or other objects with
lengths OA, OB, and OC.
circular bottoms.

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