9TH CBSE lines and angles introduction ppt BY RAMBABU SIRIPURAPU

1. MATHS TEACHER

2. MIND MAP
LINES AND ANGLES
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INTRODUCTION
A Point A Line
A line
segment
A ray
An
angle

3. A point
A point: Euclid originally defined the point as "that which has no part".
An exact location. It has no size, only position. Points usually have a
name, often a letter like "A", or even "W"

4. A line: Euclid described a line as "breathless length“.
"The line is the first species of quantity, which has only one dimension,
namely length, without any width nor depth, and is nothing else than
the flow or run of the point which will leave from its imaginary moving
some vestige in length, exempt of any width. The straight line is that
which is equally extended between its points”
CONSTRUCTIONS
a line is denoted by Sometimes small letters l, m, n, etc.

5. A line segment : a part (or portion) of a line with two end points is
called a line-segment. The line segment AB is denoted by .
CONSTRUCTIONS
.

6. A ray: a part of a line with one end point is called a ray
CONSTRUCTIONS

7. An angle: An angle is formed when two rays originate
from the same end point.
The rays making an angle are called the arms of the angle and the
end point is called the vertex of the angle.
CONSTRUCTIONS
Obtuse angle
Acute angle