From India
Harish-Chandra
He trained as a physicist under Paul Dirac before switching to mathematics.
His work on the symmetries of Lie groups now shapes much of number theory and physics. The Harish-Chandra Research Institute in Prayagraj bears his name.
Unknown author, CC BY 4.0, via Wikimedia Commons (resized)
Where you’ll meet Harish-Chandra here
Algebra
They turn up beside problems and lessons on these topics.
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Carl Friedrich Gauss
At 19 he showed that a regular 17-sided polygon can be drawn with ruler and compass, and reportedly wanted one on his tombstone.
The story of him adding 1 to 100 in seconds is probably embellished, but he called quadratic reciprocity his “golden theorem” and proved it several ways.
Christian Albrecht Jensen, Public domain, via Wikimedia Commons