If you add all three interior angle measures together in a triangle it will always equal 180°.. To find a third angle you will subtract the sum of the two given angles from 180°. Look at the 3 examples below.
Now let's look at what to do when we are given 2 angles but we are missing the 3rd angle.
Step 1: add the two angles that you are given together Step 2: subtract your answer from 180 |
Example 1:
Example 2:
Example 3:
The key to finding the missing angle measure of a triangle is to remember that the sum of the interior angles of any triangle is always 180°. If you know 2 angles then you can subtract their sum from 180° to find the measure of the 3rd angle.
Related Links: Math Geometry Topics Classifying Triangles by Angles |