Witch of Agnesi

curve

Also known as: versiera

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Last updated

July 15, 2026

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The Witch of Agnesi is a plane cubic curve with the equation (x^2y = 4a^2(2a - y)). This curve is symmetric about the y-axis and approaches the x-axis as an asymptote.1

The curve is named after Maria Gaetana Agnesi, an Italian mathematician. Her 1748 work, Instituzioni analitiche ad uso della gioventù italiana, included a discussion of this cubic curve, which was known in Italian as versiera. This term was mistakenly translated into English as "Witch of Agnesi" due to a confusion with the word for "witch". Agnesi was a pioneering figure, recognized as one of the first women to achieve a reputation in mathematics in the Western world.2

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Maria Gaetana Agnesi
…into English as the “Witch of Agnesi.” The French Academy of Sciences, in its review of the Instituzioni, stated that: “We regard it as the most complete and best made treatise.” Pope Benedict XIV was similarly impressed and appointed Agnesi professor of mathematics at the University of Bologna in…
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…into English as the “Witch of Agnesi.” The French Academy of Sciences, in its review of the Instituzioni, stated that: “We regard it as the most complete and best made treatise.” Pope Benedict XIV was similarly impressed and appointed Agnesi professor of mathematics at the University of Bologna in…
Read More