Types of Triangles - Lessons

Lesson Icon


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.

Sponsored Links

Why icon

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

You can learn more about these triangles in the lessons below.

a triangle has 3 vertices and 3 sides
Lesson Icon

Math Video Transcript

This video is an introduction to types of triangles.

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

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

We will learn the details in the upcoming lessons.

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

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.

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

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

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

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

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.

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

Topic Lessons