Use the slider at the bottom to change the amplitude (change a) or period (change b) or phase shift (change c).
You can change the function to a*sin(b*x+c). (You must have the brackets and "*" for multiply.) Click "New Function" to load your changes.
Applet by David Eck and team from the Hobart and William Smith Colleges.
Sorry about the slow load time for this applet - it is pretty big...