Page 187 - Start Up Mathematics_5

14

Circle

Let's Recall …

• All points which are equidistant from a given fixed point, when joined
together form a circle.

• A circle is a closed curve figure. It has no corners or sides.
• The distance of the centre from any point on
the boundary of the circle is called the radius C D O → centre
of the circle. OA and OB are radii of the given A O B OA, OB → radii
circle. AB → diameter
CD → chord
• The fixed point is called the centre of the Fig. 14.1
circle. In the given figure, O is the centre of the
circle.

• A line segment joining any two points on the circle and passing through the centre is
called the diameter of the circle. AB is the diameter of the given circle (Fig. 14.1).

• Diameter = 2 × radius
• Any line segment joining any two points on a circle is called the chord of the circle. In the
given figure, CD is the chord of the circle.

• Diameter is the longest chord of a circle.

1 Find the diameter of the circles whose radii are given below.

(a) 3 cm (b) 5 cm (c) 6 cm

2 Find the radii of the circles whose diameters are given below.

(a) 10 cm (b) 18 cm (c) 22 cm

Arc of a Circle
Take any two points on a circle say L and M. The part of the curve of the circle O
between L and M is called the arc. LM is one of the arcs of the given circle.
It is written as LM.
L M
Drawing a Circle of the Given Radius

We already know how to draw circles using round objects like bangles coins and with the
help of a compass. Now we will learn to draw circle of given radius using a compass and
scale.

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