Assessment and Learning in Knowledge Spaces (ALEKS) Basic Math Placement Practice Test

When finding a missing angle in a triangle, what is the first step?

1. Measure the longest side

2. Subtract the known angles from 180 degrees

3. Add all known angles together

4. Use the Pythagorean theorem

The correct answer is: Subtract the known angles from 180 degrees

The correct choice is to subtract the known angles from 180 degrees. When working with a triangle, the fundamental property to remember is that the sum of all interior angles in any triangle always equals 180 degrees. If two angles are known, you can easily find the missing angle by subtracting the sum of those two known angles from 180. This straightforward approach allows for an efficient calculation and ensures the properties of the triangle remain intact. Measuring the longest side pertains more to understanding the triangle’s dimensions rather than the angles and will not directly help in determining a missing angle. Adding all known angles together can be part of the process, but it does not directly lead to finding the missing angle without the context of the 180-degree total rule. Using the Pythagorean theorem is relevant in right triangles to relate the lengths of the sides, but it does not apply to finding angles unless you're given specific side lengths and need to determine angles based on those lengths.