I love using Geogebra! Take a look at the diagram below (use the slider to change the value of n) and then think about how difficult this one simple interactive diagram would be to recreate without the technology.
For more Geogebra resources, either check out the official Geogebra website (http://www.geogebra.org/) or the awesome resources shared below to get a feel for what you can do with Geogebra.
http://www.ualberta.ca/~urban/Projects/Math/Tech%20in%20Math.htm by @stefras
http://mrhonner.com/2011/06/19/pendulum-animation/ by @MrHonner
http://www.geogebra.org/en/upload/index.php?&direction=0&order=&directory=english/Daniel_A_Kaufmann by @dak721