 # Interior Angles Of A Triangle

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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. 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

Example:

Find the value of x in the following triangle. Solution:

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.
Example:
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?
Example:
1. Write an equation and solve for the unknown.
2. Substitute your answer into each expression to determine the measure of the angles.
Using the sum of the interior angles of a triangle, write an equation and solve for the unknown

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