### Unit 2: Parallel and Perpendicular Lines

Simply put, parallel lines are lines in a plane that do not intersect, while perpendicular lines are lines that intersect at a right angle (90°). Parallel and perpendicular lines are all around us. For example, railroad tracks, iron fencing, latticework, and kitchen tables all have parallel and/or perpendicular lines.

Have you ever looked at a tile floor that has an intricate pattern of crisscrossing lines? The pattern has to be carefully replicated, following special rules. When parallel lines cross other lines, they create their own set of special rules, which may be used in making these patterns. In this unit, you will learn what happens when parallel lines cross other lines and how all the created angles relate to each other.

**Completing this unit should take you approximately 11 hours.**