More Lessons for Geometry
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.
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.
+ 24° + 32° = 180° (sum of angles is 180°)
+ 56° = 180°
= 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
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