From the history of maths
Archimedes
Using 96-sided polygons he trapped π between 3 10/71 and 3 1/7.
He asked for a sphere inside a cylinder on his tomb, to mark his proof that the sphere fills two-thirds of it.
Painted in 1620; an imagined likeness. Domenico Fetti, Public domain, via Wikimedia Commons
Where you’ll meet Archimedes here
GeometryCalculus
They turn up beside problems and lessons on these topics.
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Euclid
His Elements was used as a textbook for more than two thousand years.
Book IX contains the classic proof that there are infinitely many primes.
Painted c. 1630; an imagined likeness. Jusepe de Ribera, Public domain, via Wikimedia Commons