# Triangle Sum Theorem Calculator

**The triangle sum theorem calculator** is a convenient tool to help you calculate an **unknown angle value** in a triangle, given two angles. Are you wondering what the triangle angle sum theorem is? Wonder no more; come along and learn **how to use the triangle sum theorem** to find the triangle angle you're looking for! 👩🏫

## Sum of angles in a triangle - What is the triangle sum theorem

According to **the triangle angle sum theorem,** the sum of all interior angles in a triangle equals **180°:**

`α + β + γ = 180°`

For instance, if you wanted to determine the unknown angle **α** in a triangle, you would use the triangle angle sum theorem in the following way:

`α = 180° - γ - β`

(in degrees)`α = π - γ - β`

(in radians)

You can also save time and trust the Omni triangle sum theorem calculator to do your work!

## How do I use the triangle sum theorem calculator?

Using a triangle sum theorem calculator is very straightforward! Just enter **two known interior angles** of a triangle in the tool. The calculator will tell you the value of a third angle according to the triangle interior angle sum theorem.

You can also change units of measurement for angles as per your convenience!

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## FAQ

### How do I calculate the third angle in a triangle if two other angles are 40° and 75°?

To calculate the **third angle** in a triangle if two other angles are 40° and 75°:

**Add 40 to 75;**in other words,**sum**two known interior angles of a triangle.**Take the sum**calculated in the previous step, and**subtract it from 180.**- That's all! The value of a third angle is
**66°.**

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

According to **the triangle angle sum theorem,** the sum of all interior angles in a triangle equals **180°.**