What is a question about this article? If the question is unanswerable, say "unanswerable".

Feynman attended Far Rockaway High School, a school in Far Rockaway, Queens also attended by fellow Nobel laureates Burton Richter and Baruch Samuel Blumberg. Upon starting high school, Feynman was quickly promoted into a higher math class. An unspecified school-administered IQ test estimated his IQ at 123—high, but "merely respectable" according to biographer James Gleick. When he turned 15, he taught himself trigonometry, advanced algebra, infinite series, analytic geometry, and both differential and integral calculus. In high school he was developing the mathematical intuition behind his Taylor series of mathematical operators. Before entering college, he was experimenting with and deriving mathematical topics such as the half-derivative using his own notation.

What did Feynman derive only after college?
unanswerable