In a triangle there are two kinds of angles:

The interior angles are formed by two sides.

The exterior angles are formed on one side and its extension.

Properties of the Angles of a Triangle

1. The sum of the interior angles of a triangle equals 180°.

A + B + C = 180º

2.  The value of an exterior angle of a triangle equals the sum of the two nonadjacent interior angles.

α = B + C

3.   The interior and exterior angles of a triangle at a particular vertex are supplementary, that is to say, they add up 180º.

α = 180º - A


Types of Triangles by Angles

Acute Triangle

An acute triangle has three acute angles.

Right Triangle

A right triangle has a right angle.

The longest side of the triangle is called the hypotenuse.

The shorter sides of the triangle are the legs or catheti (singular: cathetus).

Obtuse Triangle

An obtuse triangle has an obtuse angle.

Did you like the article?

1 Star2 Stars3 Stars4 Stars5 Stars (1 votes, average: 5.00 out of 5)


I am passionate about travelling and currently live and work in Paris. I like to spend my time reading, gardening, running, learning languages and exploring new places.

Did you like
this resource?


Download it in pdf format by simply entering your e-mail!

{{ downloadEmailSaved }}

Your email is not valid

Leave a Reply

Notify of