Hi Xavier. Thanks the question. Visit mathigon.org/pd and open the Geometry tutorial. At the bottom of that page, you'll see a video on how to add a variety of labels and measurements to constructions.

For labels on a pie chart, you can add a text box on top of the pie chart. We are working on automatic labels to pie charts, but in the meantime, you can use a text box. Hope this helps. Thanks for your interest in Mathigon!

David Poras Thank you so much Dave! All sorted now, the video was spot on, very easy with the $a and %l handles. As far as the pie chart is concerned, it is exactly what I had assumed. I had done labels directly but I wanted to make sure I hadn't missed out a trick about automatic import of the labels. Now I know it is not a feature yet... Thanks again and take care. Xavier