**Unit Overview:**

This unit focuses on the relationships of transformations and the properties of parallel lines. These two subjects are linked together because vertical angles, corresponding angles, alternate interior angles, …etc. can be described using transformations. These properties are, then, used to prove theorems about lines and angles. The combination of these topics use deductive reasoning from the properties of parallel lines will lead the proof of the Triangle Angle Sum Theorem. In order for this unit to be successful, students need to have the main definitions of basic geometry terms. After this unit, students will be able to prove congruencies of geometric figures using the foundation of this unit.

**Enduring Understanding:**

- Objects in space can be oriented in an infinite number of ways to prove congruence.
- Properties of parallel lines cut by a transversal are preserved through different transformations.

**Essential Questions:**

- How can you use the concept of transformations to prove the relationship of angle pairs of parallel lines cut by a transversal?
- How can you apply parallel lines cut by a transversal to prove the Triangle Angle Sum Theorem?