### Types of Triangles - Lessons

#### Introduction

This page contains the list of lessons on types of triangles. It also gives you a quick introduction on triangles. Each lesson consists of a math video, study tips and practice questions.

#### Lesson Description

A triangle is a polygon with three vertices and three sides (edges). It has three internal angles. When we add all the internal angles together, we will definitely get 180°.

The video below will give you a quick introduction to the following types of triangles:

• Acute triangle
• Right triangle
• Obtuse triangle
• Isosceles triangle
• Equilateral triangle
• Scalene triangle

#### Math Video Transcript

00:00:03.230
This video is an introduction to types of triangles.

00:00:09.070
A triangle is a polygon, with 3 vertices, and 3 sides.

00:00:17.120
Now, let's have a quick look, at the different triangles.

00:00:23.100
We will learn the details in the upcoming lessons.

00:00:27.240
Now, if we classify triangles by internal angles, this triangle will be an acute triangle.

00:00:35.150
Now, when I move this vertex to the left, we can see that this triangle becomes a right triangle, when the angle at vertex B is 90 degrees.

00:00:47.240
As we move vertex 'A' further to the left, this triangle becomes an obtuse triangle.

00:00:55.180
Now, let's classify triangles, by relative lengths of sides.

00:01:02.000
Let's move this vertex. When this triangle has 2 sides of equal length, it is called an isosceles triangle.

00:01:16.230
Next, if all the sides of the triangle have the same length, it is an equilateral triangle.

00:01:25.050
Let's move the vertex 'A' around. Alright, if none of the sides of the triangle have the same length, it is called a 'scalene' triangle.

00:01:39.190
That is all for the introduction. The lessons below will explain these triangles in detail.