Page 85 - Start Up Mathematics_6

Let’s define a circle and learn about its related terms.

A circle is a set of points in a plane whose distance from a fixed point always remains constant.

Centre of a circle O

The fixed point O is the centre of the circle.

Radius of a circle

The line segment joining the centre of the circle to any point on it is O
called the radius of the circle. In the adjoining figure, OP is the radius P
of the circle.

Diameter of a circle
The line segment passing through the centre of the circle and having
its end points on the circle is called its diameter. In the adjoining O
figure, AB is the diameter of the circle. A B

Relation between radius and diameter of a circle
1
Diameter = 2 × Radius or Radius = Diameter
2 P Q

O S
Chord of a circle
The line segment formed by joining any two points on the circle is R
called its chord. In the adjoining figure, PQ and RS are two chords.

Diameter is the longest chord of a circle.

Secant of a circle

The line intersecting the circle at two points is called the secant of

the circle. In the adjoining figure, MN is a secant.
N
Arc of a circle
M
The part of the circle between any two points on it is known as
the arc of the circle. Symbolically, an arc is written as APB or O
APB. If the arc is smaller than half of the circle, it is called a A B
minor arc and if it is greater than half of the circle, it is called
a major arc. P Minor arc

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