Page 162 - Math Skill - 5

160 Maths

P Q Chord of a Circle
A B
X
A line segment whose end points lie on a circle is called a chord. In the
O figure, O is the centre of the circle. PQ, AB and XY are the chords. The
Y diameter of a circle is the longest chord.

Semi-circle

Half of a circle is called a semi-circle. There are two semi-circles Semi-circle
in a circle.

Circumference of a Circle
The distance around the circle is called as circumference. Length of the circumference of a circle
is called its perimeter.

Arc of a Circle X B

Any part of a circle is called its arc. The longer arc is called the major arc A
and the shorter arc is called the minor arc. An arc is denoted by the symbol O

. In the figure, AXB is a minor arc, whereas AYB is a major arc.

Y

Concentric Circles
We can draw unlimited circles of different radii from a given centre. Circles with
the same centre and different radii are called concentric circles.

A dart board is an example of concentric circles with bull’s eye at the centre.

Drawing a Circle of Given Radius
A ruler and compass are used to draw circle. Let us draw a circle of radius 3.5 cm by following
these steps:

Step 1: Fix a sharp pencil in the compass and measure the
distance of 3.5 cm using a ruler as shown here.

Step 2: Mark any point O on the plane of the paper and rest the metal tip
of the compass firmly at O.

O A
Step 3: Hold the head of the compass and rotate it to trace the circle of
radius 3.5 cm.

Hence, the circle with centre O and radius OA = 3.5 cm is the required circle.