The diagram shows two parallel lines and a transversal.[br][br]Click and drag the points A, B, and D to change the slope of the parallel lines and the transversal. Pay careful attention to what happens between the measures of the angles shown when the slopes of these lines are changed.[br][br]To investigate other angle pairs, select one of the "show different angle pair" boxes. To best see the relationship, have only one box checked at a time.

What is the name of the angle pair shown?[br][br]Does there appear to be a relationship between the measures of the angles shown? If so, what is it?