Revision Notes on Line Segment, Ray, and Line
Learning Goal
Plane
A solid has a surface which may be flat or curved.
The flat surface is called plane surface.
A plan surface has no boundary.
Point
A geometrical element which has no dimensions (length &breadth) is called point.
Line segment: – A shape joining two points is called line segment.
Line segment AB is denoted as-
Properties of line segment: –
How to measure a line segment
To measure a line segment AB, place the zero marking of the ruler along the beginning of the line and measure its length accordingly.
In the figure given above, the length of line segment AB is 8 cm.
1. Construction of line segment if the length is known
Draw a line segment of 5 cm.
To draw a line segment of a particular length, we need a compass and a ruler.
Step 1: First of all draw a line l of any length and mark a point named A on it.
Step 2: Measure the length of 5 cm by putting the compass on the ruler. Put the pointer on 0 and open the compass till 5 cm on the ruler.
Step 3: Put the pointer at point A on the line and draw an arc of 5 cm which intersects the line at B.
Step 4: Hence the line segment of 5 cm is
Ray – A line segment which is extended by one side is called ray.
Ray AB is denoted as-
Properties of ray: –
Note- Unlimited rays can be drawn from a given point.
Line: – A line segment which is extended by both sides is called line.
Line AB is denoted as-
Properties of line: –
Note-
1. Unlimited lines can be pass from a given point.
2. One lines can be pass from two given point.
Intersecting Lines
If two lines cut each other than they are called intersecting lines.
That common point is called a Point of Intersection.
Here, line ‘l’ and ‘m’ intersect each other at point C.
Parallel Lines
If perpendicular distance between the two lines at any point is same than they are called parallel lines.
Parallel Lines never meet with each other.
Note- Two lines in a plane either intersect at exactly one points or are parallel.
Concurrent Lines
If three or more lines in a plane pass through same point than they are called concurrent lines.
The point is called point of concurrence of the given lines.
Collinear Points
Three or more points in a plane are called collinear points if they all lie on a same line.
Noncollinear Points
Three or more points in a plane are called noncollinear points if they all do not lie on a same line.
Distinction between a line, a ray and a line segment
1. Construction of line segment if the length is known
Draw a line segment of 5 cm.
To draw a line segment of a particular length, we need a compass and a ruler.
Step 1: First of all draw a line l of any length and mark a point named A on it.
Step 2: Measure the length of 5 cm by putting the compass on the ruler. Put the pointer on 0 and open the compass till 5 cm on the ruler.
Step 3: Put the pointer at point A on the line and draw an arc of 5 cm which intersects the line at B.
Step 4: Hence the line segment of 5 cm is
2. Construction of a copy of a given line segment
To make a copy of a line segment, there are three methods-
1. Measure the length of the given line segment using a ruler and draw the line segment of the same length with the ruler only.
2. Take a transparent sheet and trace the given line on another part of the paper.
3. These methods are not very accurate so we can use a ruler and compass to make an accurate line segment.
Draw a copy of the line segment
Step 1: is the given line segment whose length is known.
Step 2: Use the compass and put the pointer on A. open the compass to place the pencil side on point B. Now the open compass is of the same length as given
Step 3: Draw a new line l and mark a point C on it. Put the pointer on the point C.
Step 4: Using the same radius draw an arc on line l which cuts the line at the point D.