Parallel vs. Non-Parallel

 A Line Crosses A Pair of Parallel Lines

 

    If a set of 2 parallel lines, line l and line m, are crossed or cut by another line, line n, we say "a set of parallel lines are cut by a transversal."

    Each of the parallel lines cut by the transversal has 4 angles surrounding the intersection.

 

    These are matched in measure and position with a counterpart at the other parallel line.

 

    At each of the parallel lines, there are two pairs of vertical angles. Each angle in the pair is congruent to the other angle in the pair.

 

 1  4, angle 1 is congruent to angle 4.

 2  3, angle 2 is congruent to angle 3.

 

 5  8, angle 5 is congruent to angle 8.

 6  7, angle 6 is congruent to angle 7.

                                                 Parallel Lines Cut by a Transversal 

Non-Parallel Lines Cut by a Transversal

Transversal

A line that cuts across a set of lines or the side of a plane figure. Transversals often cut across parallel lines.