Angles and Parallel Lines

This investigation shows that when two parallel lines are cut by another line (a transversal), corresponding and alternate angles are equal, and co-interior angles are supplementary (add to 180°)
Corresponding angles are on the same side of the transversal and face the same direction:





















Alternate angles are on opposite sides of the transversal and face opposite directions:


















Co-interior angles are on the same side of the transversal but face opposite directions: