 # Revision Notes For CBSE Class 9 Math Chapter -6 Lines and Angles

Lines and Angles are the two basic elements of geometry. If the lines or line segments intersect, then the angles are formed.

Lines are the straight figures, made up of infinite points, extending infinitely in both the directions. They have negligible depth or width. There are four types of lines: horizontal line, vertical line, perpendicular, and parallel lines.

An angle is a figure formed from the two rays emerging from a common endpoint.

Listed below are types of angles:

• Acute angle – 0 to 90 degrees.
• Right angle- 90-degree angle.
• Obtuse angle- 90 to 180 degrees.
• Straight angle- 180-degree angle.

## Frequently asked Questions on CBSE Class 9 Maths Notes Chapter 6: Lines and Angles

### What are the different types of angles?

1. Acute Angles.2. Obtuse Angles.3. Right Angles.4. Straight Angles.5. Reflex Angles.6. Full Rotation.

### What is the definition of a ‘Degree’?

A unit of measurement, especially used in the measurement of angles.

### What is a ‘Perpendicular line’?

Perpendicular lines are lines that intersect at a right (90 degrees) angle.