This document covers different topics in geometry including points, lines, line segments, rays, angles, and measuring angles. It defines each term and provides examples. Points have position but no size, a line extends indefinitely, a line segment connects two points, a ray has an endpoint and extends in one direction, and an angle is formed by two rays with a common endpoint. The document explains how to measure angles using a protractor and the degree unit, and provides practice examples of finding the measure of different angles.

1. CH 7
SUBTOPIC 1 -POINT, LINES, LINE SEGMENT AND RAY
SUBTOPIC 2- ANGLE, NAMING AN ANGLE
SUBTOPIC 3 - MEASURING AN ANGLE

2. WARM - UP
Look at he following picture and list out all the shapes that you see in it.
Try to observe geometrical shapes in everything that you see around.

4. ★ A point shows a definite
position or location, which
cannot be moved.
★ It is represented by a dot (.)
★ A point has no length, no
breadth and no thickness.
★ Points are named using single
capital letters.
N.B
A
B
P
Q
L
M
X
Z

5. ★ A collection of points makes a
line. It extends endlessly or
indefinitely in both the
directions.
★ A line has no end points.
★ It has only length which cannot
be measured.
★ It has no width. N.B
★ Its length
LINE
Line AB can be written as
20/6/2021 (MATHS )

6. LINE SEGMENT ❏ A part of a line is called a line
segment.
❏ It has two endpoints.
❏ It has a definite length, but no
breadth or thickness.
❏ The length of a line segment cannot
be increased or decreased.
❏ It is the shortest distance
between two points.
N.B

7. RAY ★ A ray is a part of a line that
has one end point and can
be extended in the other
direction indefinitely.
★ The fixed end point is called
initial point of the ray.
★ The length of a ray cannot be
measured. N.B

8. CONCURRENT LINES N.B
★ Three or more lines which meets
at one common point are called
concurrent lines.
★ You can draw infinite number of
lines passing through a point.

9. COLLINEAR AND NON-COLLINEAR POINTS
COLLINEAR: N.B
Three or more points which lie on the same
line are known as collinear points.
NON-COLLINEAR POINTS:
The points that do not lie on the same
line are known as non-collinear points.
Here, points B, C, F, E are non-collinear
points.

10. PLANE ★ A plane is a flat
two-dimensional surface that
can be extended endlessly in
all the directions.
★ A plane is actually a collection
of an infinite number of points.
★ It contains an infinite number of
lines, line segments and rays.
★ A plane can be determined by
three non-collinear points or a
line and a point.
N.B

11. REFER THE BELOW VIDEO TO KNOW MORE ABOUT POINTS, LINES,LINE SEGMENTS AND ANGLES
https://www.youtube.com/watch?v=dFPwrBVocpY

12. PRACTICE TIME N.B

13. ANGLE
An angle is formed by
two rays with common
initial point.
N.B

14. ∠
∠

16. PRACTICE TIME N.B
1.

17. INTERIOR AND EXTERIOR OF AN ANGLE N.B
An angle has two parts- Interior and exterior.
★ The points lying inside the angle form the interior of the
angle.
★ The points lying outside the angle form the exterior of the
angle.
In the adjoining figure points,
➢ X, Y and Z lie in the interior of ∠ PQR.
➢ A, B nd C lie in the exterior of ∠ PQR.

18. PRACTICE TIME N.B

19. MEASURING ANGLES
● A tool that is used to measure angles is called protractor.
● Degree is the basic unit of measurement of an angle. It is denoted by °.
● The straight edge of a protractor is called the baseline.
● The curved edge of a protractor has two scales - inner scale and outer scale.
➢ The inner scale is marked from 0° to 180° from right to left.
➢ The outer scale is marked from 0° to 180° from left to right.
➢ Each division of a scale represents one degree.
N.B

23. Example 1: Measure∠XYZ using a protractor.
To measure ∠XYZ proceed as follows.
Step 1: Place the protractor on angle ∠XYZ in such a way that
its centre lies on the vertex Y and its base line coincides with the arm YZ.
Step 2: Read the mark on the inner scale through which the
arm YX is passing.
As the arm YX is passing through the mark 50 °,
so the measure of ∠XYZ is 50°.
ANSWER: ∠XYZ = 50°.

28. Example 2: Measure∠AOB using a protractor.
To measure ∠AOB proceed as follows.
Step 1: Place the protractor on angle ∠AOB in such a way that
its centre lies on the vertex O and its base line coincides with the arm OA.
Step 2: Read the mark on the outer scale through which
the arm OB is passing.
As the arm OB is passing through the mark 45°,
so the measure of ∠AOB is 45°.
ANSWER: ∠AOB = 45°.

29. Refer the below video to know how to measure an angle.
https://www.youtube.com/watch?v=il22YcHDfeE