Same Side Interior

Drag point D around and notice the angle measures changing. Drag D so that the lines appear to be as parallel as possible. Record the angle measures. Drag D so that the lines will eventually intersect on the right. Record the angle measures. Drag D so that the lines will eventually intersect on the left. Record the angle measures. Discuss the relationship between the angle measures and the "parallelness" of the lines. What seems to be the case?