Types Of Triangles

A triangle is a specific type of polygon having only three sides and three angle. As the name suggest, it tri-angle is a type of polygon having three angles. The sum of all interior angles of a triangle will always add up to 180 degrees.

Triangles can be broadly classified into two types, i.e.

  • Triangle Based on the lengths of sides
  • Triangle Based on interior angles

These have been explained below.

Types of Triangles : Based on the Length of Sides

According to the lengths of their sides, triangles can be classified into three types:

  • Equilateral Triangle

In such a triangle, all the side lengths are equal. In such a case, each of the interior angles will have a measure of 60 degrees. The figure given below illustrates an equilateral triangle.

Equilateral Triangle

  • Isosceles Triangle

In an isosceles triangle, two of the three side lengths will be equal to each other. An isosceles triangle has two equal sides and two equal angles. The angles opposite the equal sides will be equal to each other. The figure given below illustrates an isosceles triangle.

Isosceles Triangle

  • Scalene Triangle

A scalene triangle has all side lengths of different measures. No side will be equal in length to any of the other sides in such a triangle. In a scalene triangle, all the interior angles will also be different. The figure given below illustrates a scalene triangle. You can see how none of the sides are equal in length.

Scalene Triangle

Types of Triangles : Based on interior angles

  • Right Triangle

A right triangle is a triangle in which one of the angles is 90 degrees. In such a triangle, the side opposite to the right angle (90-degree angle) will be the longest side, and is called the hypotenuse. You may come across triangle types with combined names like right isosceles triangle and such, but this only implies that the triangle has two equal sides with one of the interior angles being 90 degrees. The figure given below illustrates a right triangle.

Right Triangle

  • Acute Triangles

If a triangle has all three interior angles which are acute, then it is an acute triangle. In other words, if all interior angles are less than 90 degrees, then it is an acute triangle. The figure given below illustrates an acute triangle.

Acute Angle

  • Obtuse Triangles

If a triangle is such that one of its three interior angles has a measure greater than 90 degrees, then it is an obtuse triangle. In other words, if one of the angles in a triangle is an obtuse angle, then the triangle is called an obtuse triangle or an obtuse angled triangle. The figure given below illustrates an obtuse triangle.

Obtuse Triangles

To learn more about types of triangles and different topics download BYJU’S – The Learning App from Google Play Store and watch interactive videos. Also, take free tests to practice for exams.


Practise This Question

Shreya measured the angles in a triangle which came out to be  60°, 50°, and 70° respectively. Now she wants to know what type of triangle it is.
Can you tell what type of triangle it is?