Below is a sample graph about waves I made in about 5 minutes for a Grade 8 Science inquiry into wave properties. I was able to add some text questions on the side with the sliders. The equation was from an example and I simply changed a few of the variables so that amplitude was (a) and period was (p). Now students can explore the way the ways change before I ever tell them anything about how amplitude and period are defined. My guess is that 5 minutes of prep, and 5 minutes of playing around with students will result in far greater conceptual understanding than I could achieve with them in 2-3 periods of manual graphing, reading, and discussion. Personally I'd have the metal slinkies out next for them to replicate and explain the phenomenon next!
Desmos is pretty amazing even if you never tweak a thing, but just use their provided templates. You have to make sure to click the drop down menu in the very top right (3 lines right above the + symbol). In the example below I would have students play around with the sliders before I ever defined y, m, and b and instead let the students inquire into them, and then use a follow up discussion to clarify any misconceptions.
The Common Ratio: http://thecommonratio.blogspot.com/2013/10/des-man-vodcasts.html where Ange lays out an awesome inquiry with her Grade 11s using DesMan inspire by....
Finding Ways to Nguyen Students Over: http://fawnnguyen.com/2013/03/20/des-man.aspx, and on to the tool...
DesMan Teacher Edition: https://class.desmos.com/desman