Explain Basic Concepts of Parallel Lines ?

Parallel lines are defined in section 1.2 and we use "//" to denote it. From the definition, we can get the following two consequences by observation.

1. Parts (segments or rays) of parallel lines are parallel.

2. Extensions of parallel segments or rays are parallel.

Definition 1

A transversal is a line that intersects two coplanar lines at two distinct points. The region between the two lines is the interior of the figure. The rest of the plane is the exterior.

Example 1

In this figure, which line is an transversal, which region is interior and which one is exterior?
Answer Line n is a transversal regious a, c, e, and f are exterior regions b and d are interior

Definition 2

The distance between two parallel lines is the distance from any point on one line to the other line.