# Revision Notes For CBSE Class 9 Math Chapter -7 Triangles

A triangle is a plane figure with three straight sides and three angles. The sum of angles of a triangle is equal to 180 degrees and the exterior angles of a triangle are always equal to 360 degrees. In a triangle, the sum of the angles is always greater than the length of the third angle. The area of a triangle is given by the formulae:

Â½ * base * height.

A triangle is classified into different types based on their sides and angles.

• Equilateral Triangle
• Isosceles triangle
• Scalene Triangle
• Acute angled Triangle
• Right angle Triangle
• Obtuse-angled Triangle

Details about Chapter 7 of Class 9 Maths are given below:

## Frequently asked Questions on CBSE Class 9 Maths Notes Chapter 7: Triangles

### What are the types of triangles?

There are three main types of triangle based on the length of the sides: equilateral, isosceles and scalene.

### What are â€˜Similar trianglesâ€™?

Triangles that have the same shape, but their sizes may vary are called as similar triangles.

### What is an â€˜exteriorâ€™ angle?

The angle between any side of a shape, and a line extended from the next side is called as the â€˜exterior angleâ€™.