Page 164 - New Medley 5 Semester 2

We come across many familiar things with circular shapes like coins,
bangles, wheels, CDs, plates, rings, etc. A simple closed curve or a round
shape strikes in our mind whenever we talk about a circle.

We can easily draw a circle by sketching the outline of any object discussed

above.

In addition, paths traced by moving ends of a fan, running the hands of a

clock, etc., can be considered as circles. Hence, we can define a circle as:

A path traced by a point which remains at a fixed distance from a fixed

point on a given plane is called a circle where the fixed point (centre)
and the moving point both must lie in the same plane.

Parts of a Circle

Let us recall the terms associated with a circle which we had studied in

the previous class.
P C
  Circumference: It is the boundary of the circle. Q
Chord
In other words, the distance covered round Radius
the circle is called its circumference. O
A B
  Centre: The fi xed point from which every Diameter

point of the circle is equidistant is called the

centre of the circle. In the given figure, point

O reflects the centre of the circle.
R
  Radius: The distance between centre and any point lying on the boundary

is called the radius of the circle. In the given figure, OA, OB and OC
all are radii of the circle.

  Diameter: A line segment passing through the centre and touching the
two points on the circumference of the circle is called its diameter. In

the given figure, AOB is a diameter.

Here, Diameter = AOB = AO + OB = AO + AO = 2AO = 2 × Radius

  Chord: A line segment with end points on the circumference is called

a chord of the circle. In the given figure, AC is a chord. Also, AB is a

chord. Diameter of a circle is the longest chord.

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