In this lesson activity, students are engaged from the start. Students will use the tools of GeoGebra (a FREE, EASY-TO-USE, dynamic mathematics software application) to discover properties of tangents drawn to circles. Namely, students will discover two theorems:
1) If a line is tangent to a circle, then the radius drawn to the point of tangency is perpendicular to this tangent.
2) Tangent segments drawn to a circle (from a point outside that circle) are congruent.
The activity then leads students to another applet (available for free at http://tube.geogebra.org/m/z7QUMhmr) to provide further investigation and insight into proving the 2nd listed theorem true.