OML Search

Interior Angles Of A Triangle

Related Topics:
More Lessons for Geometry
Math Worksheets

The following diagram shows that the sum of angles in a triangle is 180°. Scroll down the page for more examples and solutions on how to find missing angles in a triangle.

Sum angles triangle

In this lesson, we will learn

  • the interior angles of a triangle
  • the properties of the interior angles of a triangle
  • how the properties can be used to find the missing angles inside a triangle.
  • how the sum of interior angles of a triangle can be used to set up equations.

Interior Angles

The interior angles of a triangle are the angles inside the triangle

Properties of Interior Angles

  • The sum of the three interior angles in a triangle is always 180°.
  • Since the interior angles add up to 180°, every angle must be less than 180°.


Find missing angles inside a triangle


Find the value of x in the following triangle.


x + 24° + 32° = 180° (sum of angles is 180°)
x + 56° = 180°
x = 180° – 56° = 124°

How to find the missing angle inside a triangle.
Find the missing angle in a triangle.
A = 15°, B = ?, C = 92°

Using Interior Angles of Triangle to set up equations

How to use the sum of the interior angles of a triangle to solve problems?
1. Write an equation and solve for the unknown.
2. Substitute your answer into each expression to determine the measure of the angles.
3. Give reasons for your answers.
Using the sum of the interior angles of a triangle, write an equation and solve for the unknown

Rotate to landscape screen format on a mobile phone or small tablet to use the Mathway widget, a free math problem solver that answers your questions with step-by-step explanations.

You can use the free Mathway calculator and problem solver below to practice Algebra or other math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.

OML Search

We welcome your feedback, comments and questions about this site or page. Please submit your feedback or enquiries via our Feedback page.

[?] Subscribe To This Site

follow us in feedly
Add to My Yahoo!
Add to My MSN
Subscribe with Bloglines