Maria Gaetana Agnesi, Italian mathematician and philosopher (born 1718)

Maria Gaetana Agnesi was an Italian mathematician, philosopher, theologian, and humanitarian. She was the first woman to write a mathematics handbook, the first woman appointed as a mathematics professor at a university and the second woman appointed as a professor overall.

January 9 is the ninth day of the year in the Gregorian calendar; 356 days remain until the end of the year.