Parallel Lines and Corresponding Angles
Blue parallel lines cut across by a red transversal. 
The angle pair shown below are called corresponding angles. What do you notice about their position? Their angle measures? 
Drag points B and C to a variety of positions and note how angles p and t relate to each other.
Use the check boxes to make other pairs of corresponding angles active and see how moving B and C affect these new angle pairs. 
What can you conclude about corresponding angles?