GeoGebra Lab 11

In this lab, we will discover properties of angles formed by two lines (or segments) cut by a transversal.

1. Open GeoGebra and turn off the axes and the grid.

2. Draw two parallel lines \(AB\) and \(CD\) and a transversal \(EF\) as shown in the diagram. Construct the intersection points \(G\) and \(H\).

   
3. Measure all eight angles using the Angle tool and press ESC when you are finished.
4. Move all angle measurement labels so that they are readable.
5. Move point \(F\) on the transversal to change the orientation of the line. Note the relationships between pairs of angles.

6. Make a conjecture about the relationship between the following pairs of angles formed by parallel lines.

   • corresponding angles
   • alternate interior angles
   • same-side interior angles
   • alternate exterior angles
7. Write your conjecture about corresponding angles as an “if-then” statement. Is the converse of this statement true?