Measurements - e-content - 8th standard - SCERT - EPC3

1. MEASUREMENTS
Mathematics
8th Standard
SCERT - Tamilnadu
DESILVA A S

2. Parts of a Circle
Center, Radius, Diameter, Chord.

3. Circle
A circle is the path traced
by a moving point so that
its distance from a fixed
point is always a constant.

4. Parts of the Circle
The fixed point of the
circle is called its
‘center’ and the constant
distance is called its
‘radius’.

5. Chord
The chord of a circle
can be defined as the
line segment joining
any two points on the
circumference of the
circle.

6. Diameter
A chord which passes
through the center of a
circle is called as a
‘diameter’.

7. Arc – Sector - Segment
• A part of the circumference of a circle is
called a circular arc.
• The plane surface that is enclosed between
two radii and the circular arc of a circle is
called a sector.
• Each part of a circle which is divided by a
chord is called a segment.

8. Parts of the Circle
Arc Sector Segment Arc-Sector-Segment

9. Central Angle
A central angle is the angle that forms
when two radii meet at the center of a
circle.
Remember that a vertex is the
point where two lines meet to form an
angle. A central angle's vertex will
always be the center point of a circle.

10. Central Angle
Th e central angle of a circle is
360°.
If a circle is divided into ‘n’ equ
al sectors, the central angle of
each of the sectors is 𝜃0
=
360
𝑛

11. Arc
Meaning

12. Sector
Meaning

13. Perimeter of a sector
P = length of the arc + length of two radii
P = l + 2r units
Perimeter of a sector,
P = l + 2r units

14. Real life examples

15. Thank you