woollymathematics.com provides access to 19th century mathematical problems, so that this invaluable knowledge will not be lost.

It all began when mathematician Daniil Rudenko was looking for findings related to his work on the
trigonometry of tetrahedra (an exercise Vladimir Drinfeld once called *“solving the Inverse Plagiarism
Problem”*). Eventually, he came across Joseph Wolstenholme's ‘Problem 13605’, published in the
*Educational Times* a few years after the author's death.

The fascinating story of Joseph Wolstenholme, Virginia Woolf, and the trigonometry of tetrahedra can be read here. Wolstenholme's theorem may be the most important finding in the trigonometry of tetrahedra, yet it has passed unnoticed by the mathematical community.

In 2023 Daniil Rudenko joined forces with Sloan Despeaux, a historian of mathematics, and Sergei
Vorobiev, Ivan Tiapin, and Sergey Serebryakov, software engineers, on a project designed to provide
access to 18,783 problems published in 815 issues of the *Educational Times* between 1848 and 1915.
Categorization of the problems and information about their authors is taken from the database created by
mathematician Raymond Clare Archibald and historian of mathematics James Tattersall, Jr.

To us, ‘forgotten’ mathematics is a source of eternal inspiration: browsing through old questions and
trying to make connections with contemporary math is absolutely fascinating. Hidden gems in the
collection of problems include tricky puzzles suited to mathematical olympiads and elegant theorems of
algebraic geometry that have never made it into the literature. We think the *Educational Times*
problem
database could prove to be an invaluable resource for historians of mathematics, olympiad trainers,
mathematical enthusiasts and working mathematicians.

We would love to hear from you! Please share your feedback and discoveries with us at [email protected].