Today during Algebra II, while I had students working with Free Graph Calculator before having them do the same set of equations on Desmos, I actually clicked on a tab I didn't usually do and discovered that it has instructional screens on trig: period and amplitude, phase, all trig functions, wave interference and the unit circle. Then there are instructional screens for conic sections dealing with Circle, Parabola and Focus, Ellipse with Foci, and the Hyperbola. Then there is a section on Polar Graphing with Polar Rose, Logarithmic Spiral, Polar Conic Sections, and Limacon. I like that there are four screens on transformations followed by 4 screens on calculus.
Each screen allows the student to explore and change certain variables so they are able to see what happens with the changes to the graph. Now that I know about this section, I can assign various screens to my students as an exploration for all my classes. I also hope to post some pictures later today.