# CBSE Class 9: Lines and Angles - Basics Terms and Definition

In this video we will learn the basic terms and definitions of the chapter lines and angles from CBSE Class 9 Mathematics. This lecture by the expert teacher will definitely help you build a strong hold over the basics of lines and angles and proceed to the concepts of this topic more efficiently.

Nov 23, 2017 09:56 IST
Class 9 Llines & Angles: Baisc Terms and definitions

In this video you will learn about the topics basic terms and definitions of the chapter lines and angles.

• Collinear Points: Three or more points are said to be collinear, if a line passes through all three points.
• Ray: Ray is a part of line, which has one the end point and can be extended indefinitely on the other end.
• When two rays have a common initial point they are said to have formed an angle.
• The angle is measured in degrees or radians.
• Acute angle: If the measure of an angle lies between 0o and 90o.
• Right angle: If the measure of an angle is equal to 90o.
• Obtuse Angle: If the measure of an angle lies between 90o and 180o.
• Straight angle: If the measure of an angle is equal to 180o.
• Reflex angle: If the measure of an angle is greater than 180o but less than 360o.

CBSE Class 9: Heron’s Formula - Applications of Heron’s Formula

CBSE Class 9: Lines and Angles - Types of Angles