Check out JSXGraph:
http://jsxgraph.uni-bayreuth.de/wp/
It's mobile friendly so long as the user's browser supports canvas (in my experience with it). It supports multi-touch devices too, but I haven't verified that.
Re:Plotly.js Open-Source Announcement
by QuasarLogic on Tuesday November 17, 2015 @02:46PM
(#10583486)
You could compute a few [x,y] values for an equation y=f(x) and plot them using any line chart plotting library
Any suggestions on available libraries, or am I better to start from scratch on this?