I gave the students a worksheet on solving systems of equations using elimination. The first thing I had the students do was to graph the two equations on Desmos and write down the point of interception. This app is quite good in that it shows a dot where the lines cross and if you tap the dot, it will display the coordinates in (x,y) form. The other day one of my students stumbled across a section with examples of lines, parabolas, trig, conic sections, polar graphing, transformations and calculus. Each of these topics has subtopics. I looked at the trig section and it has period and amplitude, phase, all the trig functions, wave interference and the unit circle. I tapped on period and amplitude and a small dialog box came up with an sample problem and the graph. It allows you to explore the graph by changing values of the period and amplitudes and the graph automatically adjusts. This would allow a student to actually put values in of real problems to see them solved.

You can add an expression, text or table. Furthermore, you can change the window settings. The more I use this particular graphing program, the more I see uses for it next year in my classes. The bad thing is that you do not have to rewrite equations into the slope intercept form to use it.