# Parallel and Perpendicular Lines

Parallel and perpendicular lines are sets of lines which display a specific relationship between them. Parallel lines are lines that do not intersect and the perpendicular lines intersect at right angles. The following diagram shows the locations of the houses of three friends.

It can be seen that Cindy's and Rudy's houses are situated in parallel streets, while Nancy's house is on a street which is perpendicular to both these streets. This illustrates how the relationship of two lines to a third line can lead to the relationship between the two lines.

1. In a plane if two lines are perpendicular to the same line, then they are parallel to each other.

2. If two lines are parallel to the same line, then they are parallel to each other.