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Published online by Cambridge University Press: 21 October 2019
Andrew Palfreyman’s article [1] reminds us of the result(1)$${\rm{ta}}{{\rm{n}}^{{\rm{ - 1}}}}{\rm{+ta}}{{\rm{n}}^{{\rm{ - 1}}}}\,2{\rm{+ta}}{{\rm{n}}^{{\rm{ - 1}}}}{\rm{ 3= }}\,\pi {\rm{, }}$$having been set the challenge of finding the value of the left-hand side by his head of department at the start of a departmental meeting.