Zip file contains ALL student-centered discovery activities listed on my TpT website. In these activities, students use GeoGebra as the platform in order to discover the following theorems:
If a quadrilateral has both pairs of opposite sides congruent (part 1), one pair of opposite sides both congruent and parallel (part 2), both pairs of opposite angles congruent (part 3), and diagonals that bisect each other (part 4), then that quadrilateral is a parallelogram.
The GeoGebra platform for discoveries for part 3 an be found here: http://tube.geogebra.org/material/simple/id/2695783
The GeoGebra platform for parts (1), (2), & (4) can be found here:
Save $1.50 by purchasing this entire zip file vs. buying parts (1) - (3) separately. (Part 4 is available for free download.)