# Interior and Exterior Triangle Angles Calculator

Table of contents

How do I find interior angles of a triangle? Triangle sum theoremHow do I find exterior angles of a triangle?What is the sum of the exterior angles of a triangle?How does the interior and exterior angles calculator work?Other related calculatorsFAQsWelcome to the Omni **interior and exterior triangle angles calculator,** the convenient tool that will help you calculate the interior and exterior angles of a triangle. Are you wondering **how to find the exterior and interior angles of a triangle?** Then you're at the right place. Come along, and learn about the triangle sum theorem and the exterior angle theorem! 👩🏫

## How do I find interior angles of a triangle? Triangle sum theorem

**Interior angles** of a triangle are angles found inside the shape. According to **the triangle angle sum theorem,** sum of interior angles of a triangle always equals **180°:**

`a + b + c = 180°`

For example, if you were trying to calculate an unknown interior angle `a`

, you would utilize the triangle angle sum theorem in the following way:

`a = 180° - b - c`

(in degrees)`a = π - b - c`

(in radians)

Keep on reading to learn about the definition of the exterior angle of a triangle!

## How do I find exterior angles of a triangle?

What is the **definition** of **the exterior angle** of a triangle? If you were to extend any side of a triangle, the angle outside the triangle, adjacent to an interior angle, is an exterior angle of a triangle. Each triangle has six exterior angles, and two angles at each vertex are equal in value.

To find exterior angles of a triangle, you can use **the exterior angle theorem.** The exterior angle theorem states that **the exterior angle is equal to the sum of the triangle's two opposite interior angles**.

For instance, if you wanted to calculate **the exterior angle d,** you would use the following formula:

`d = a + b`

## What is the sum of the exterior angles of a triangle?

The sum of **exterior angles** of a triangle always adds up to **360°,** while the sum of **interior angles** of a triangle equals **180°.**

## How does the interior and exterior angles calculator work?

Using **the interior and exterior triangle angles calculator** is very straightforward!

Just enter two of any interior angles of the triangle, and the calculator will determine all remaining unknown values of interior and exterior angles.

Don't forget to change **units of measurement** for angles as per your convenience!

### How do I find the third interior angle in a triangle if two other angles are 45° and 90°?

To find the third interior angle in a triangle if two other angles are 45° and 90°:

- Add 45 to 90; in other words, calculate the
**sum**of two known interior angles of a triangle. - Take the number you computed in the previous step, and
**subtract it from 180.** - Voila! The value of a third angle is
**45°.**

### How do I find interior and exterior angles of a triangle?

- To find
**an interior angle**of a triangle, take the sum two known interior angles of a triangle and**subtract the number from 180.** - To find
**an exterior angle**of a triangle, simply calculate the**sum**two opposite interior angles of a triangle.