1. Introduction to Lines and Angles

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.