A special Christmas-themed edition of Oxford Calculus from University of Oxford Mathematician Dr Tom Crawford. Featuring 3D graphs and the divergence of a function. We focus on two functions: first plotting the 3D graph of a cone given by z = – (x² + y²)^1/2, before calculating the partial derivatives of a function of two variables and combining them to find the divergence.

You can investigate both functions for yourself using the Maple Calculator App. You can download the app for free from Google Play and the App Store.