You have probably seen something like this in your cup of tea (or coffee, I don’t discriminate) before:
I’ve written a very short activity that has a little bit of conversion between forms of graphs and introduces how to import a picture into Desmos that could easily be used in the classroom. It actually works surprisingly well using Desmos on a phone.
If you wish to use it please download from here: Tea Cup Cardioid
And if you want to know more of the physics and maths behind this I recommend this Chalkdust article from Dominika Vasilkova (@dragon_dodo) – it’s a great article!