Properties of Parallel Lines

In this investigation, you'll discover relationships among the angles formed when parallel lines are intersected by a third line, called a transversal.

Sketch and Investigate

1. Construct line AB and point C, not on line AB. 2. Construct a line parallel to line AB through point C. 3. Construct line CA. Drag points C and A to make sure the three lines are attached at those points. 4. Construct points D, E, F, G, and H as shown.