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Line Segment

A part of a line with two endpoints is called a line segment. In the following figure, AB is a line
segment. It is denoted by AB or BA, where A and B are its end points.

A B
Take a thin thread and hold its two ends. Stretch it without slack. This represents a line segment.

The edge of a book, a tube light, etc. are examples of line segments.
Knowledge Desk

A bar above AB, i.e., AB
to denote line segment
was first used in 1647 by
Ray Bonaventura Cavalieri.

A part of a line with one end point is called a ray. It goes endlessly in one
direction. A ray AB is shown in the figure given alongside. It is denoted A B

by AB, where A is the starting point and point B lies on the path of the ray.
Here are some models of a ray.

Ray

Example 1: Look at the figure given alongside and name the following:
(a) Six points (b) A line A

(c) All possible rays (d) Six line segments B
Solution: (a) Six points are: A, O, B, C, D and E. O C

E
(b) A line is DB. D

(c) All possible rays are OA OB OC OD ED BD DE EB, , , , , , , .
(d) Six line segments are DE EO OB DO EB DB, , , , , .
Example 2: How many lines can pass through (a) one given point? (b) two given points?
Solution: (a) Infinitely many lines can pass through one given point.
l
m

n
p

(b) Only one line can pass through two given points. A B

29 Lines and Angles