shewhomust | The Witch of Agnesi and other tales of the unexpected

Earlier this week,

durham_rambler asked me if I had prepared for this week's pub quiz by brushing up on the works of Roald Dahl. No, I said, we can safely rely on the rest of the team (who are younger than us, and some of whom have children) for that.

As it turned out, there wasn't a round - or even an individual question - which required familiarity with the works of Roald Dahl. But there was a hidden theme running through the entire quiz. This is a trick of which Frank, one of the two quiz-setters who alternate at the Elm Tree pub quiz, is fond (and so am I). We started, as ever, with the word round, which concerned words of Norwegian origin, round two was a set of questions about foxes, and so on.

A set of questions about witches included "In which area of study might you come across the Witch of Agnesi?" We didn't know. I thought it sounded ever so faintly familiar, and one or two of us thought it might be mathematics, but the mathematicians among us denied all knowledge of it, so we went for philosophy instead. Mathematics would have been the correct answer. Frank read out what the term meant: something to do with dropping a perpendicular to the radius of a circle? No, that can't be right. But I was sufficiently interested to go away and look it up, and the answer is surprisingly interesting, for two reasons.

The first is that "the Witch of Agnesi?" is a mistranslation: she isn't a witch at all, she's a sine curve (a 'versed sine curve', which means nothing to me).

The second, and I can't help wondering whether this factor influenced that mistranslation, is that this particular curve was studied by, and named for, Maria Agnesi in her book Instituzioni analitiche ad uso della gioventú italiana (published in 1748, the first surviving mathematical work written by a woman).

I son't know which of these things delights me more.