How it works ?
Definition: A transversal is a line that intersects 2 other lines at 2 distinct points.
In the applet, the dashed line below is a transversal. (Actually, each of the three lines displayed below is a transversal.)
When a transversal intersects 2 other lines, special names are given to certain pairs of angles. These angle pairs are called corresponding angles, alternate interior angles, alternate exterior angles, same-side interior angles, and same-side exterior angles.