The sundial problem and a cheat sheet by Russell Goyder

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From Russell Goyder ( @russellgoyder ) on discord:

I'd like to share something that I think some people here might find interesting. About 20 years ago, for fun, I analyzed sundials (using GA, paper here: https://russellgoyder.github.io/sundial-latex/) and used Maple and https://www.mrao.cam.ac.uk/~maja1/software/GA/ to help with the calculation.

I had reason to dust it off recently and made a version using SymPy and GAlgebra: https://russellgoyder.github.io/sundial/. During that process, I created a cheat sheet: https://russellgoyder.github.io/geometric-algebra-cheat-sheet/. I hope the paper, notebook and cheat sheet are useful, interesting or both to someone here, and welcome any feedback you would like to give.

It would be nice to validate the GAlgebra against these resources.