1. Lesson 9

1.10. Lesson 9 Summary

Module 2: Lesson 9

Module 2: Logic and Geometry

 

Lesson 9 Summary
 
This is a cartoon of a right angle lawyer (90 degrees) trying to prove to a judge that his clients (two acute angles measuring 48 degrees and 42 degrees) do in fact make a right (a 90 angle).

Hemera/Thinkstock

 

The theorem that the sum of the interior angles in a triangle is 180° has been given to you in previous math courses. In this lesson you applied the properties of angles you learned in this module to prove that the sum of the interior angles in a triangle is 180°.

 

The properties of angles are useful for solving problems. As you have seen, many items in design involve triangles and parallel lines. An understanding of how the properties of angles can be used to determine that two lines are parallel can be used to verify design plans. In some instances, the properties can be combined in a variety of ways to solve the same problem.

 

In Lesson 10 you will continue to work with properties of angles. This time, you will use the properties of angles to prove that two triangles are congruent.