INTRODUCTION 
1.    Point: 
      A fine dot made by a sharp pencil or a geometrical figure having no length, breadth and height as called a point.

2.    Line segment
      If we join two fixed points then the figure formed is called line segment.

3.    Line
      If we extend the two end points of a line segment in either direction endlessly then it is called a line.
      It has no definite length.

4.    Ray
      If we extend one end point of a line segment endlessly then it is called a ray.

5.    Angle
      An angle is formed by intersecting two rays. The intersection point is the common initial point of these two rays which is called as vertex of the angle. We use the symbol ‘ ’ to denote the measure of the angle
    •    An angle is an inclination between two rays with the same initial point.

 

 

 

 

 

In this fig. the angles are  

°°

°

°

°

°°

Chapter 5

Lines and Angles

Introduction to Lines and Angles

Line:
A line is a straight figure which doesn’t have an endpoint and extends infinitely in opposite directions.

Ray:
A ray is a straight line, which starts from a fixed point and moves in one direction.

Line Segment
A portion of the line formed with two definite points is called a Line Segment. A line is a one-dimensional figure and has no thickness.

Angle
When we join two line segments at a single point, an angle is formed, or we can say, an Angle is a combination of two line segments at a common endpoint. This common point is called Vertex of the angle and the two line segments are sides or arms of the angle formed.
 

Types of Angles

There are basically 6 types of angles which are:

  1. Acute Angle: If an angle is less than 90 degrees, then it is called an Acute angle
  2. Obtuse Angle: If an angle is more than 90 degrees, then it is called Obtuse Angle
  3. Right Angle: If an angle is exactly at 90 degrees, then it is called Right Angle.
  4. Straight Angle: If an angle is exactly 180 degrees, then it is called Straight Angle.
  5. Reflex Angle: If the angle is more than 180 degree but less than 270 degrees, it is denoted as a Reflex angle.
  6. Full Angle: A 360-degree angle is called a Full angle.

 

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clas 7 math
Medha Sharma

Course : CBSE Class 7

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